[MM-57067][MM-57006][MM-57328] Acknowledge websocket POSTED events that may result in a notification on the web client (#26604)

* Acknowledge POSTED events that may result in a notification

* Remove temporary metrics

* Add Desktop App support

* Merge'd

* Add some tests

* PR feedback

* Rework window is focused check

* Oops

* Move mentions/followers ACK to posted ACK broadcast hook

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/platform/client/src/websocket.ts

@@ -412,6 +412,18 @@ export default class WebSocketClient {
         this.sendMessage('user_update_active_status', data, callback);
     }
 
+    acknowledgePostedNotification(postId: string, result: 'error' | 'not_sent' | 'unsupported' | 'success', reason?: string, postedData?: string) {
+        const data = {
+            post_id: postId,
+            user_agent: window.navigator.userAgent,
+            result,
+            reason,
+            data: postedData,
+        };
+
+        this.sendMessage('posted_notify_ack', data);
+    }
+
     getStatuses(callback?: () => void) {
         this.sendMessage('get_statuses', null, callback);
     }