/// Defines the HTTP configuration for an API service. It contains a list of
/// [HttpRule][google.api.HttpRule], each specifying the mapping of an RPC method
/// to one or more HTTP REST API methods.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct Http {
    /// A list of HTTP configuration rules that apply to individual API methods.
    ///
    /// **NOTE:** All service configuration rules follow "last one wins" order.
    #[prost(message, repeated, tag = "1")]
    pub rules: ::std::vec::Vec<HttpRule>,
    /// When set to true, URL path parameters will be fully URI-decoded except in
    /// cases of single segment matches in reserved expansion, where "%2F" will be
    /// left encoded.
    ///
    /// The default behavior is to not decode RFC 6570 reserved characters in multi
    /// segment matches.
    #[prost(bool, tag = "2")]
    pub fully_decode_reserved_expansion: bool,
}
/// # gRPC Transcoding
///
/// gRPC Transcoding is a feature for mapping between a gRPC method and one or
/// more HTTP REST endpoints. It allows developers to build a single API service
/// that supports both gRPC APIs and REST APIs. Many systems, including [Google
/// APIs](https://github.com/googleapis/googleapis),
/// [Cloud Endpoints](https://cloud.google.com/endpoints), [gRPC
/// Gateway](https://github.com/grpc-ecosystem/grpc-gateway),
/// and [Envoy](https://github.com/envoyproxy/envoy) proxy support this feature
/// and use it for large scale production services.
///
/// `HttpRule` defines the schema of the gRPC/REST mapping. The mapping specifies
/// how different portions of the gRPC request message are mapped to the URL
/// path, URL query parameters, and HTTP request body. It also controls how the
/// gRPC response message is mapped to the HTTP response body. `HttpRule` is
/// typically specified as an `google.api.http` annotation on the gRPC method.
///
/// Each mapping specifies a URL path template and an HTTP method. The path
/// template may refer to one or more fields in the gRPC request message, as long
/// as each field is a non-repeated field with a primitive (non-message) type.
/// The path template controls how fields of the request message are mapped to
/// the URL path.
///
/// Example:
///
///     service Messaging {
///       rpc GetMessage(GetMessageRequest) returns (Message) {
///         option (google.api.http) = {
///             get: "/v1/{name=messages/*}"
///         };
///       }
///     }
///     message GetMessageRequest {
///       string name = 1; // Mapped to URL path.
///     }
///     message Message {
///       string text = 1; // The resource content.
///     }
///
/// This enables an HTTP REST to gRPC mapping as below:
///
/// HTTP | gRPC
/// -----|-----
/// `GET /v1/messages/123456`  | `GetMessage(name: "messages/123456")`
///
/// Any fields in the request message which are not bound by the path template
/// automatically become HTTP query parameters if there is no HTTP request body.
/// For example:
///
///     service Messaging {
///       rpc GetMessage(GetMessageRequest) returns (Message) {
///         option (google.api.http) = {
///             get:"/v1/messages/{message_id}"
///         };
///       }
///     }
///     message GetMessageRequest {
///       message SubMessage {
///         string subfield = 1;
///       }
///       string message_id = 1; // Mapped to URL path.
///       int64 revision = 2;    // Mapped to URL query parameter `revision`.
///       SubMessage sub = 3;    // Mapped to URL query parameter `sub.subfield`.
///     }
///
/// This enables a HTTP JSON to RPC mapping as below:
///
/// HTTP | gRPC
/// -----|-----
/// `GET /v1/messages/123456?revision=2&sub.subfield=foo` |
/// `GetMessage(message_id: "123456" revision: 2 sub: SubMessage(subfield:
/// "foo"))`
///
/// Note that fields which are mapped to URL query parameters must have a
/// primitive type or a repeated primitive type or a non-repeated message type.
/// In the case of a repeated type, the parameter can be repeated in the URL
/// as `...?param=A&param=B`. In the case of a message type, each field of the
/// message is mapped to a separate parameter, such as
/// `...?foo.a=A&foo.b=B&foo.c=C`.
///
/// For HTTP methods that allow a request body, the `body` field
/// specifies the mapping. Consider a REST update method on the
/// message resource collection:
///
///     service Messaging {
///       rpc UpdateMessage(UpdateMessageRequest) returns (Message) {
///         option (google.api.http) = {
///           patch: "/v1/messages/{message_id}"
///           body: "message"
///         };
///       }
///     }
///     message UpdateMessageRequest {
///       string message_id = 1; // mapped to the URL
///       Message message = 2;   // mapped to the body
///     }
///
/// The following HTTP JSON to RPC mapping is enabled, where the
/// representation of the JSON in the request body is determined by
/// protos JSON encoding:
///
/// HTTP | gRPC
/// -----|-----
/// `PATCH /v1/messages/123456 { "text": "Hi!" }` | `UpdateMessage(message_id:
/// "123456" message { text: "Hi!" })`
///
/// The special name `*` can be used in the body mapping to define that
/// every field not bound by the path template should be mapped to the
/// request body.  This enables the following alternative definition of
/// the update method:
///
///     service Messaging {
///       rpc UpdateMessage(Message) returns (Message) {
///         option (google.api.http) = {
///           patch: "/v1/messages/{message_id}"
///           body: "*"
///         };
///       }
///     }
///     message Message {
///       string message_id = 1;
///       string text = 2;
///     }
///
///
/// The following HTTP JSON to RPC mapping is enabled:
///
/// HTTP | gRPC
/// -----|-----
/// `PATCH /v1/messages/123456 { "text": "Hi!" }` | `UpdateMessage(message_id:
/// "123456" text: "Hi!")`
///
/// Note that when using `*` in the body mapping, it is not possible to
/// have HTTP parameters, as all fields not bound by the path end in
/// the body. This makes this option more rarely used in practice when
/// defining REST APIs. The common usage of `*` is in custom methods
/// which don't use the URL at all for transferring data.
///
/// It is possible to define multiple HTTP methods for one RPC by using
/// the `additional_bindings` option. Example:
///
///     service Messaging {
///       rpc GetMessage(GetMessageRequest) returns (Message) {
///         option (google.api.http) = {
///           get: "/v1/messages/{message_id}"
///           additional_bindings {
///             get: "/v1/users/{user_id}/messages/{message_id}"
///           }
///         };
///       }
///     }
///     message GetMessageRequest {
///       string message_id = 1;
///       string user_id = 2;
///     }
///
/// This enables the following two alternative HTTP JSON to RPC mappings:
///
/// HTTP | gRPC
/// -----|-----
/// `GET /v1/messages/123456` | `GetMessage(message_id: "123456")`
/// `GET /v1/users/me/messages/123456` | `GetMessage(user_id: "me" message_id:
/// "123456")`
///
/// ## Rules for HTTP mapping
///
/// 1. Leaf request fields (recursive expansion nested messages in the request
///    message) are classified into three categories:
///    - Fields referred by the path template. They are passed via the URL path.
///    - Fields referred by the [HttpRule.body][google.api.HttpRule.body]. They are passed via the HTTP
///      request body.
///    - All other fields are passed via the URL query parameters, and the
///      parameter name is the field path in the request message. A repeated
///      field can be represented as multiple query parameters under the same
///      name.
///  2. If [HttpRule.body][google.api.HttpRule.body] is "*", there is no URL query parameter, all fields
///     are passed via URL path and HTTP request body.
///  3. If [HttpRule.body][google.api.HttpRule.body] is omitted, there is no HTTP request body, all
///     fields are passed via URL path and URL query parameters.
///
/// ### Path template syntax
///
///     Template = "/" Segments [ Verb ] ;
///     Segments = Segment { "/" Segment } ;
///     Segment  = "*" | "**" | LITERAL | Variable ;
///     Variable = "{" FieldPath [ "=" Segments ] "}" ;
///     FieldPath = IDENT { "." IDENT } ;
///     Verb     = ":" LITERAL ;
///
/// The syntax `*` matches a single URL path segment. The syntax `**` matches
/// zero or more URL path segments, which must be the last part of the URL path
/// except the `Verb`.
///
/// The syntax `Variable` matches part of the URL path as specified by its
/// template. A variable template must not contain other variables. If a variable
/// matches a single path segment, its template may be omitted, e.g. `{var}`
/// is equivalent to `{var=*}`.
///
/// The syntax `LITERAL` matches literal text in the URL path. If the `LITERAL`
/// contains any reserved character, such characters should be percent-encoded
/// before the matching.
///
/// If a variable contains exactly one path segment, such as `"{var}"` or
/// `"{var=*}"`, when such a variable is expanded into a URL path on the client
/// side, all characters except `[-_.~0-9a-zA-Z]` are percent-encoded. The
/// server side does the reverse decoding. Such variables show up in the
/// [Discovery
/// Document](https://developers.google.com/discovery/v1/reference/apis) as
/// `{var}`.
///
/// If a variable contains multiple path segments, such as `"{var=foo/*}"`
/// or `"{var=**}"`, when such a variable is expanded into a URL path on the
/// client side, all characters except `[-_.~/0-9a-zA-Z]` are percent-encoded.
/// The server side does the reverse decoding, except "%2F" and "%2f" are left
/// unchanged. Such variables show up in the
/// [Discovery
/// Document](https://developers.google.com/discovery/v1/reference/apis) as
/// `{+var}`.
///
/// ## Using gRPC API Service Configuration
///
/// gRPC API Service Configuration (service config) is a configuration language
/// for configuring a gRPC service to become a user-facing product. The
/// service config is simply the YAML representation of the `google.api.Service`
/// proto message.
///
/// As an alternative to annotating your proto file, you can configure gRPC
/// transcoding in your service config YAML files. You do this by specifying a
/// `HttpRule` that maps the gRPC method to a REST endpoint, achieving the same
/// effect as the proto annotation. This can be particularly useful if you
/// have a proto that is reused in multiple services. Note that any transcoding
/// specified in the service config will override any matching transcoding
/// configuration in the proto.
///
/// Example:
///
///     http:
///       rules:
///         # Selects a gRPC method and applies HttpRule to it.
///         - selector: example.v1.Messaging.GetMessage
///           get: /v1/messages/{message_id}/{sub.subfield}
///
/// ## Special notes
///
/// When gRPC Transcoding is used to map a gRPC to JSON REST endpoints, the
/// proto to JSON conversion must follow the [proto3
/// specification](https://developers.google.com/protocol-buffers/docs/proto3#json).
///
/// While the single segment variable follows the semantics of
/// [RFC 6570](https://tools.ietf.org/html/rfc6570) Section 3.2.2 Simple String
/// Expansion, the multi segment variable **does not** follow RFC 6570 Section
/// 3.2.3 Reserved Expansion. The reason is that the Reserved Expansion
/// does not expand special characters like `?` and `#`, which would lead
/// to invalid URLs. As the result, gRPC Transcoding uses a custom encoding
/// for multi segment variables.
///
/// The path variables **must not** refer to any repeated or mapped field,
/// because client libraries are not capable of handling such variable expansion.
///
/// The path variables **must not** capture the leading "/" character. The reason
/// is that the most common use case "{var}" does not capture the leading "/"
/// character. For consistency, all path variables must share the same behavior.
///
/// Repeated message fields must not be mapped to URL query parameters, because
/// no client library can support such complicated mapping.
///
/// If an API needs to use a JSON array for request or response body, it can map
/// the request or response body to a repeated field. However, some gRPC
/// Transcoding implementations may not support this feature.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct HttpRule {
    /// Selects a method to which this rule applies.
    ///
    /// Refer to [selector][google.api.DocumentationRule.selector] for syntax details.
    #[prost(string, tag = "1")]
    pub selector: std::string::String,
    /// The name of the request field whose value is mapped to the HTTP request
    /// body, or `*` for mapping all request fields not captured by the path
    /// pattern to the HTTP body, or omitted for not having any HTTP request body.
    ///
    /// NOTE: the referred field must be present at the top-level of the request
    /// message type.
    #[prost(string, tag = "7")]
    pub body: std::string::String,
    /// Optional. The name of the response field whose value is mapped to the HTTP
    /// response body. When omitted, the entire response message will be used
    /// as the HTTP response body.
    ///
    /// NOTE: The referred field must be present at the top-level of the response
    /// message type.
    #[prost(string, tag = "12")]
    pub response_body: std::string::String,
    /// Additional HTTP bindings for the selector. Nested bindings must
    /// not contain an `additional_bindings` field themselves (that is,
    /// the nesting may only be one level deep).
    #[prost(message, repeated, tag = "11")]
    pub additional_bindings: ::std::vec::Vec<HttpRule>,
    /// Determines the URL pattern is matched by this rules. This pattern can be
    /// used with any of the {get|put|post|delete|patch} methods. A custom method
    /// can be defined using the 'custom' field.
    #[prost(oneof = "http_rule::Pattern", tags = "2, 3, 4, 5, 6, 8")]
    pub pattern: ::std::option::Option<http_rule::Pattern>,
}
pub mod http_rule {
    /// Determines the URL pattern is matched by this rules. This pattern can be
    /// used with any of the {get|put|post|delete|patch} methods. A custom method
    /// can be defined using the 'custom' field.
    #[derive(Clone, PartialEq, ::prost::Oneof)]
    pub enum Pattern {
        /// Maps to HTTP GET. Used for listing and getting information about
        /// resources.
        #[prost(string, tag = "2")]
        Get(std::string::String),
        /// Maps to HTTP PUT. Used for replacing a resource.
        #[prost(string, tag = "3")]
        Put(std::string::String),
        /// Maps to HTTP POST. Used for creating a resource or performing an action.
        #[prost(string, tag = "4")]
        Post(std::string::String),
        /// Maps to HTTP DELETE. Used for deleting a resource.
        #[prost(string, tag = "5")]
        Delete(std::string::String),
        /// Maps to HTTP PATCH. Used for updating a resource.
        #[prost(string, tag = "6")]
        Patch(std::string::String),
        /// The custom pattern is used for specifying an HTTP method that is not
        /// included in the `pattern` field, such as HEAD, or "*" to leave the
        /// HTTP method unspecified for this rule. The wild-card rule is useful
        /// for services that provide content to Web (HTML) clients.
        #[prost(message, tag = "8")]
        Custom(super::CustomHttpPattern),
    }
}
/// A custom pattern is used for defining custom HTTP verb.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct CustomHttpPattern {
    /// The name of this custom HTTP verb.
    #[prost(string, tag = "1")]
    pub kind: std::string::String,
    /// The path matched by this custom verb.
    #[prost(string, tag = "2")]
    pub path: std::string::String,
}
/// An indicator of the behavior of a given field (for example, that a field
/// is required in requests, or given as output but ignored as input).
/// This **does not** change the behavior in protocol buffers itself; it only
/// denotes the behavior and may affect how API tooling handles the field.
///
/// Note: This enum **may** receive new values in the future.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
#[repr(i32)]
pub enum FieldBehavior {
    /// Conventional default for enums. Do not use this.
    Unspecified = 0,
    /// Specifically denotes a field as optional.
    /// While all fields in protocol buffers are optional, this may be specified
    /// for emphasis if appropriate.
    Optional = 1,
    /// Denotes a field as required.
    /// This indicates that the field **must** be provided as part of the request,
    /// and failure to do so will cause an error (usually `INVALID_ARGUMENT`).
    Required = 2,
    /// Denotes a field as output only.
    /// This indicates that the field is provided in responses, but including the
    /// field in a request does nothing (the server *must* ignore it and
    /// *must not* throw an error as a result of the field's presence).
    OutputOnly = 3,
    /// Denotes a field as input only.
    /// This indicates that the field is provided in requests, and the
    /// corresponding field is not included in output.
    InputOnly = 4,
    /// Denotes a field as immutable.
    /// This indicates that the field may be set once in a request to create a
    /// resource, but may not be changed thereafter.
    Immutable = 5,
}
/// A simple descriptor of a resource type.
///
/// ResourceDescriptor annotates a resource message (either by means of a
/// protobuf annotation or use in the service config), and associates the
/// resource's schema, the resource type, and the pattern of the resource name.
///
/// Example:
///
///     message Topic {
///       // Indicates this message defines a resource schema.
///       // Declares the resource type in the format of {service}/{kind}.
///       // For Kubernetes resources, the format is {api group}/{kind}.
///       option (google.api.resource) = {
///         type: "pubsub.googleapis.com/Topic"
///         name_descriptor: {
///           pattern: "projects/{project}/topics/{topic}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///           parent_name_extractor: "projects/{project}"
///         }
///       };
///     }
///
/// The ResourceDescriptor Yaml config will look like:
///
///     resources:
///     - type: "pubsub.googleapis.com/Topic"
///       name_descriptor:
///         - pattern: "projects/{project}/topics/{topic}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///           parent_name_extractor: "projects/{project}"
///
/// Sometimes, resources have multiple patterns, typically because they can
/// live under multiple parents.
///
/// Example:
///
///     message LogEntry {
///       option (google.api.resource) = {
///         type: "logging.googleapis.com/LogEntry"
///         name_descriptor: {
///           pattern: "projects/{project}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///           parent_name_extractor: "projects/{project}"
///         }
///         name_descriptor: {
///           pattern: "folders/{folder}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Folder"
///           parent_name_extractor: "folders/{folder}"
///         }
///         name_descriptor: {
///           pattern: "organizations/{organization}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Organization"
///           parent_name_extractor: "organizations/{organization}"
///         }
///         name_descriptor: {
///           pattern: "billingAccounts/{billing_account}/logs/{log}"
///           parent_type: "billing.googleapis.com/BillingAccount"
///           parent_name_extractor: "billingAccounts/{billing_account}"
///         }
///       };
///     }
///
/// The ResourceDescriptor Yaml config will look like:
///
///     resources:
///     - type: 'logging.googleapis.com/LogEntry'
///       name_descriptor:
///         - pattern: "projects/{project}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///           parent_name_extractor: "projects/{project}"
///         - pattern: "folders/{folder}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Folder"
///           parent_name_extractor: "folders/{folder}"
///         - pattern: "organizations/{organization}/logs/{log}"
///           parent_type: "cloudresourcemanager.googleapis.com/Organization"
///           parent_name_extractor: "organizations/{organization}"
///         - pattern: "billingAccounts/{billing_account}/logs/{log}"
///           parent_type: "billing.googleapis.com/BillingAccount"
///           parent_name_extractor: "billingAccounts/{billing_account}"
///
/// For flexible resources, the resource name doesn't contain parent names, but
/// the resource itself has parents for policy evaluation.
///
/// Example:
///
///     message Shelf {
///       option (google.api.resource) = {
///         type: "library.googleapis.com/Shelf"
///         name_descriptor: {
///           pattern: "shelves/{shelf}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///         }
///         name_descriptor: {
///           pattern: "shelves/{shelf}"
///           parent_type: "cloudresourcemanager.googleapis.com/Folder"
///         }
///       };
///     }
///
/// The ResourceDescriptor Yaml config will look like:
///
///     resources:
///     - type: 'library.googleapis.com/Shelf'
///       name_descriptor:
///         - pattern: "shelves/{shelf}"
///           parent_type: "cloudresourcemanager.googleapis.com/Project"
///         - pattern: "shelves/{shelf}"
///           parent_type: "cloudresourcemanager.googleapis.com/Folder"
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct ResourceDescriptor {
    /// The resource type. It must be in the format of
    /// {service_name}/{resource_type_kind}. The `resource_type_kind` must be
    /// singular and must not include version numbers.
    ///
    /// Example: `storage.googleapis.com/Bucket`
    ///
    /// The value of the resource_type_kind must follow the regular expression
    /// /[A-Za-z][a-zA-Z0-9]+/. It should start with an upper case character and
    /// should use PascalCase (UpperCamelCase). The maximum number of
    /// characters allowed for the `resource_type_kind` is 100.
    #[prost(string, tag = "1")]
    pub r#type: std::string::String,
    /// Optional. The relative resource name pattern associated with this resource
    /// type. The DNS prefix of the full resource name shouldn't be specified here.
    ///
    /// The path pattern must follow the syntax, which aligns with HTTP binding
    /// syntax:
    ///
    ///     Template = Segment { "/" Segment } ;
    ///     Segment = LITERAL | Variable ;
    ///     Variable = "{" LITERAL "}" ;
    ///
    /// Examples:
    ///
    ///     - "projects/{project}/topics/{topic}"
    ///     - "projects/{project}/knowledgeBases/{knowledge_base}"
    ///
    /// The components in braces correspond to the IDs for each resource in the
    /// hierarchy. It is expected that, if multiple patterns are provided,
    /// the same component name (e.g. "project") refers to IDs of the same
    /// type of resource.
    #[prost(string, repeated, tag = "2")]
    pub pattern: ::std::vec::Vec<std::string::String>,
    /// Optional. The field on the resource that designates the resource name
    /// field. If omitted, this is assumed to be "name".
    #[prost(string, tag = "3")]
    pub name_field: std::string::String,
    /// Optional. The historical or future-looking state of the resource pattern.
    ///
    /// Example:
    ///
    ///     // The InspectTemplate message originally only supported resource
    ///     // names with organization, and project was added later.
    ///     message InspectTemplate {
    ///       option (google.api.resource) = {
    ///         type: "dlp.googleapis.com/InspectTemplate"
    ///         pattern:
    ///         "organizations/{organization}/inspectTemplates/{inspect_template}"
    ///         pattern: "projects/{project}/inspectTemplates/{inspect_template}"
    ///         history: ORIGINALLY_SINGLE_PATTERN
    ///       };
    ///     }
    #[prost(enumeration = "resource_descriptor::History", tag = "4")]
    pub history: i32,
    /// The plural name used in the resource name and permission names, such as
    /// 'projects' for the resource name of 'projects/{project}' and the permission
    /// name of 'cloudresourcemanager.googleapis.com/projects.get'. It is the same
    /// concept of the `plural` field in k8s CRD spec
    /// https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/
    ///
    /// Note: The plural form is required even for singleton resources. See
    /// https://aip.dev/156
    #[prost(string, tag = "5")]
    pub plural: std::string::String,
    /// The same concept of the `singular` field in k8s CRD spec
    /// https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/
    /// Such as "project" for the `resourcemanager.googleapis.com/Project` type.
    #[prost(string, tag = "6")]
    pub singular: std::string::String,
}
pub mod resource_descriptor {
    /// A description of the historical or future-looking state of the
    /// resource pattern.
    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
    #[repr(i32)]
    pub enum History {
        /// The "unset" value.
        Unspecified = 0,
        /// The resource originally had one pattern and launched as such, and
        /// additional patterns were added later.
        OriginallySinglePattern = 1,
        /// The resource has one pattern, but the API owner expects to add more
        /// later. (This is the inverse of ORIGINALLY_SINGLE_PATTERN, and prevents
        /// that from being necessary once there are multiple patterns.)
        FutureMultiPattern = 2,
    }
}
/// Defines a proto annotation that describes a string field that refers to
/// an API resource.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct ResourceReference {
    /// The resource type that the annotated field references.
    ///
    /// Example:
    ///
    ///     message Subscription {
    ///       string topic = 2 [(google.api.resource_reference) = {
    ///         type: "pubsub.googleapis.com/Topic"
    ///       }];
    ///     }
    ///
    /// Occasionally, a field may reference an arbitrary resource. In this case,
    /// APIs use the special value * in their resource reference.
    ///
    /// Example:
    ///
    ///     message GetIamPolicyRequest {
    ///       string resource = 2 [(google.api.resource_reference) = {
    ///         type: "*"
    ///       }];
    ///     }
    #[prost(string, tag = "1")]
    pub r#type: std::string::String,
    /// The resource type of a child collection that the annotated field
    /// references. This is useful for annotating the `parent` field that
    /// doesn't have a fixed resource type.
    ///
    /// Example:
    ///
    ///     message ListLogEntriesRequest {
    ///       string parent = 1 [(google.api.resource_reference) = {
    ///         child_type: "logging.googleapis.com/LogEntry"
    ///       };
    ///     }
    #[prost(string, tag = "2")]
    pub child_type: std::string::String,
}
