Improve WebSocketServer Error Handling (#6230)

* Improve WebSocketServer Error Handling

Closes: https://github.com/parse-community/parse-server/issues/6173

Prevents an unhandled server rejection.

Includes an example for LiveQuery test and closing the proper connections.

Improve live query monitoring

* fix tests

src/Adapters/WebSocketServer/WSAdapter.js

@@ -13,10 +13,12 @@ export class WSAdapter extends WSSAdapter {
 
   onListen() {}
   onConnection(ws) {}
+  onError(error) {}
   start() {
     const wss = new WebSocketServer({ server: this.options.server });
     wss.on('listening', this.onListen);
     wss.on('connection', this.onConnection);
+    wss.on('error', this.onError);
   }
   close() {}
 }

src/Adapters/WebSocketServer/WSSAdapter.js

@@ -4,6 +4,7 @@
 // Adapter classes must implement the following functions:
 // * onListen()
 // * onConnection(ws)
+// * onError(error)
 // * start()
 // * close()
 //
@@ -22,6 +23,7 @@ export class WSSAdapter {
   constructor(options) {
     this.onListen = () => {};
     this.onConnection = () => {};
+    this.onError = () => {};
   }
 
   // /**
@@ -36,6 +38,13 @@ export class WSSAdapter {
   //  */
   // onConnection(ws) {}
 
+  // /**
+  //  * Emitted when error event is called.
+  //  *
+  //  * @param {Error} error - WebSocketServer error
+  //  */
+  // onError(error) {}
+
   /**
    * Initialize Connection.
    *