Add optional trigger argument to WebSocketService

src/app/services/websocket.service.ts

@@ -43,14 +43,19 @@ export class WebSocketService {
     return this.downlink.pipe(filter(message => message.key === key));
   }
 
-  public send(key: string, data: any): void {
+  public send(key: string, data?: any, trigger?: any): void {
     // If the WebSocket is not connected then the QueueingSubject will ensure
     // that messages are queued and delivered when the WebSocket reconnects.
     // A regular Subject can be used to discard messages sent when the WebSocket
     // is disconnected.
-    this.uplink.next({
-      'key': key,
-      'data': data
-    });
+    // TODO: do this nicer?
+    const message = {'key': key};
+    if (data) {
+      message['data'] = data;
+    }
+    if (trigger) {
+      message['trigger'] = trigger;
+    }
+    this.uplink.next(message);
   }
 }