[MM-45802] Clear CRT notification on deleted reply (#23568)

* reduce the counter on post deletion

* add test

* change translations

* fix collecting mentions for DMs

* add translation texts

* extract logic for getting mentions

* send WS event

* add e2e tests

* tidy mod

* WIP

* Deleting notification async

* Fixed a unit test

* Added more tests

* Updated i18n

* CI

* mattermost-server -> mattermost

* mattermost-server -> mattermost

---------

Co-authored-by: Konstantinos Pittas <konstantinos.pittas@mattermost.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/post.go

@@ -1338,6 +1338,12 @@ func (a *App) DeletePost(c request.CTX, postID, deleteByID string) (*model.Post,
 		a.deleteFlaggedPosts(post.Id)
 	})
 
+	a.Srv().Go(func() {
+		if err = a.RemoveNotifications(c, post, channel); err != nil {
+			a.Log().Error("DeletePost failed to delete notification", mlog.Err(err))
+		}
+	})
+
 	a.invalidateCacheForChannelPosts(post.ChannelId)
 
 	return post, nil