Websocket: unhandle rejection (#6418)

* Websocket: unhandle rejection

Closes: https://github.com/parse-community/parse-server/issues/6413, https://github.com/parse-community/parse-server/issues/6173
Prevent crashing on websocket error.

Bonus points to anybody who can post a specific payload that the client sends that returns an error.

* log the socket

* fix tests

* fix payload reference link

src/LiveQuery/ParseWebSocketServer.js

@@ -13,6 +13,10 @@ export class ParseWebSocketServer {
       logger.info('Parse LiveQuery Server starts running');
     };
     wss.onConnection = ws => {
+      ws.on('error', error => {
+        logger.error(error.message);
+        logger.error(JSON.stringify(ws));
+      });
       onConnect(new ParseWebSocket(ws));
       // Send ping to client periodically
       const pingIntervalId = setInterval(() => {