feat: Allows sharing of network (#16937)

build(docker): Expose mailhog port.

build(Docker): Improve wording.

build(docker): Mailhog and network changes.

    * Add mailhog container to shared network to enable connectivity
    * Configure project name for docker compose in .env sample file,
        without it the basename of the repo directory is used, which
        makes it unreachable for other services
    * Set mailhog host to mailhog (instead of localhost) if MAILHOG_HOST
      env var is set
    * Expose 1025 to enable local troubleshooting

build(docker): Update README to reflect compose changes.

server/datasources.development.js

@@ -10,7 +10,7 @@ if (!process.env.SES_ID) {
     connector: 'mail',
     transport: {
       type: 'smtp',
-      host: 'localhost',
+      host: process.env.MAILHOG_HOST || 'localhost',
       secure: false,
       port: 1025,
       tls: {
@@ -26,4 +26,5 @@ if (!process.env.SES_ID) {
 } else {
   debug('using AWS SES to deliver emails');
 }
+
 module.exports = ds;