update config_api with initialization and recovery utilities (#5523)

* update config_api with initialization and recovery utilities

* nits

* move tests to config_tests to eliminate config_api solana_runtime dependency

* fixups

programs/config_api/src/lib.rs

@@ -1,4 +1,6 @@
-use serde::Serialize;
+use bincode::{deserialize, serialize, serialized_size};
+use serde_derive::{Deserialize, Serialize};
+use solana_sdk::{account::Account, pubkey::Pubkey, short_vec};
 
 pub mod config_instruction;
 pub mod config_processor;
@@ -13,7 +15,44 @@ solana_sdk::solana_name_id!(
     "Config1111111111111111111111111111111111111"
 );
 
-pub trait ConfigState: Serialize {
+pub trait ConfigState: serde::Serialize + Default {
     /// Maximum space that the serialized representation will require
     fn max_space() -> u64;
 }
+
+/// A collection of keys to be stored in Config account data.
+#[derive(Debug, Default, Deserialize, Serialize)]
+pub struct ConfigKeys {
+    // Each key tuple comprises a unique `Pubkey` identifier,
+    // and `bool` whether that key is a signer of the data
+    #[serde(with = "short_vec")]
+    pub keys: Vec<(Pubkey, bool)>,
+}
+
+impl ConfigKeys {
+    pub fn serialized_size(keys: Vec<(Pubkey, bool)>) -> u64 {
+        serialized_size(&ConfigKeys { keys }).unwrap()
+    }
+}
+
+pub fn get_config_data(bytes: &[u8]) -> Result<&[u8], bincode::Error> {
+    deserialize::<ConfigKeys>(bytes)
+        .and_then(|keys| serialized_size(&keys))
+        .map(|offset| &bytes[offset as usize..])
+}
+
+// utility for pre-made Accounts
+pub fn create_config_account<T: ConfigState>(
+    keys: Vec<(Pubkey, bool)>,
+    config_data: &T,
+    lamports: u64,
+) -> Account {
+    let mut data = serialize(&ConfigKeys { keys }).unwrap();
+    data.extend_from_slice(&serialize(config_data).unwrap());
+    Account {
+        lamports,
+        data,
+        owner: id(),
+        ..Account::default()
+    }
+}