feat: Asynchronous initialization of Parse Server (#8232)

BREAKING CHANGE: This release introduces the asynchronous initialization of Parse Server to prevent mounting Parse Server before being ready to receive request; it changes how Parse Server is imported, initialized and started; it also removes the callback `serverStartComplete`; see the [Parse Server 6 migration guide](https://github.com/parse-community/parse-server/blob/alpha/6.0.0.md) for more details (#8232)

src/Options/Definitions.js

@@ -466,10 +466,6 @@ module.exports.ParseServerOptions = {
     env: 'PARSE_SERVER_SERVER_CLOSE_COMPLETE',
     help: 'Callback when server has closed',
   },
-  serverStartComplete: {
-    env: 'PARSE_SERVER_SERVER_START_COMPLETE',
-    help: 'Callback when server has started',
-  },
   serverURL: {
     env: 'PARSE_SERVER_URL',
     help: 'URL to your parse server with http:// or https://.',

src/Options/docs.js

@@ -85,7 +85,6 @@
  * @property {SchemaOptions} schema Defined schema
  * @property {SecurityOptions} security The security options to identify and report weak security settings.
  * @property {Function} serverCloseComplete Callback when server has closed
- * @property {Function} serverStartComplete Callback when server has started
  * @property {String} serverURL URL to your parse server with http:// or https://.
  * @property {Number} sessionLength Session duration, in seconds, defaults to 1 year
  * @property {Boolean} silent Disables console output

src/Options/index.js

@@ -271,8 +271,6 @@ export interface ParseServerOptions {
   :ENV: PARSE_SERVER_PLAYGROUND_PATH
   :DEFAULT: /playground */
   playgroundPath: ?string;
-  /* Callback when server has started */
-  serverStartComplete: ?(error: ?Error) => void;
   /* Defined schema
   :ENV: PARSE_SERVER_SCHEMA
   */