[MM-58070] Ensure the batched post handler also send websocket acknowledgements (#26938)

* [MM-58070] Ensure the batched post handler also send websocket acknowledgements

* Add ack for missing root post error

---------

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

webapp/channels/src/actions/new_post.ts

@@ -49,6 +49,9 @@ export function completePostReceive(post: Post, websocketMessageProps: NewPostMe
             const result = await dispatch(PostActions.getPostThread(post.root_id));
 
             if ('error' in result) {
+                if (websocketMessageProps.should_ack) {
+                    WebSocketClient.acknowledgePostedNotification(post.id, 'error', 'missing_root_post', result.error);
+                }
                 return {error: result.error};
             }
         }

webapp/channels/src/actions/websocket_actions.jsx

@@ -733,6 +733,12 @@ export function handleNewPostEvents(queue) {
             console.log('handleNewPostEvents - new posts received', posts);
         }
 
+        posts.forEach((post, index) => {
+            if (queue[index].data.should_ack) {
+                WebSocketClient.acknowledgePostedNotification(post.id, 'not_sent', 'too_many_posts');
+            }
+        });
+
         // Receive the posts as one continuous block since they were received within a short period
         const crtEnabled = isCollapsedThreadsEnabled(myGetState());
         const actions = posts.map((post) => receivedNewPost(post, crtEnabled));