Thread autoresponse posts with the post they are autoresponding to (#15625)

* Thread autoresponse posts with the post they are autoresponding to

* Remove unneeded if

* Remove ParentID references

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/post.go

@@ -451,7 +451,7 @@ func (a *App) handlePostEvents(post *model.Post, user *model.User, channel *mode
 
 	if post.Type != model.POST_AUTO_RESPONDER { // don't respond to an auto-responder
 		a.Srv().Go(func() {
-			_, err := a.SendAutoResponseIfNecessary(channel, user)
+			_, err := a.SendAutoResponseIfNecessary(channel, user, post)
 			if err != nil {
 				mlog.Error("Failed to send auto response", mlog.String("user_id", user.Id), mlog.String("post_id", post.Id), mlog.Err(err))
 			}