MM-37577 Do not set post id when posting a message (#5602) (#5608)

* MM-37577 Do not set post id when posting a message

* Add unit test to verify that creating a post always send an empty string as the id

(cherry picked from commit 7cdbe095a1)

Co-authored-by: Elias Nahum <nahumhbl@gmail.com>

app/mm-redux/actions/posts.test.js

@@ -38,12 +38,14 @@ describe('Actions.Posts', () => {
     it('createPost', async () => {
         const channelId = TestHelper.basicChannel.id;
         const post = TestHelper.fakePost(channelId);
+        const createPost = jest.spyOn(Client4, 'createPost');
 
         nock(Client4.getBaseRoute()).
             post('/posts').
             reply(201, {...post, id: TestHelper.generateId()});
 
         await Actions.createPost(post)(store.dispatch, store.getState);
+        expect(createPost).toHaveBeenCalledWith(expect.objectContaining({id: ''}));
 
         const state = store.getState();
         const createRequest = state.requests.posts.createPost;

app/mm-redux/actions/posts.ts

@@ -182,6 +182,7 @@ export function createPost(post: Post, files: any[] = []) {
 
         let newPost = {
             ...post,
+            id: '',
             pending_post_id: pendingPostId,
             create_at: timestamp,
             update_at: timestamp,