MM-46410: adds urgency on mention counts (#20999)

* MM-46410: adds urgency on mention counts

We have introduced priority for posts in
https://github.com/mattermost/mattermost-webapp/pull/10951.
We do need to color the mention badges in the webapp with a prominent
color when a mention is posted in an urgent message.
A thread has urgent mentions if the root post is marked as urgent, and
the replies contain mentions to the user viewing the thread.

This PR adds a column, urgentmentioncount, in channelmembers.
Furthermore when asking for team/thread mention counts, we also return
urgent mention counts for the user.

Adds a new table to hold posts priorities
Refactors priority out of the props and into the new table

We are nilifying Metadata when post.ForPlugin(), which didn't save Priority
for a post when Boards was enabled.
This commit copies metadata again to the post, so metadata are
reinstated.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Vishal Choudhary <vish9812@gmail.com>

app/user.go

@@ -2391,6 +2391,10 @@ func (a *App) ConvertBotToUser(c request.CTX, bot *model.Bot, userPatch *model.U
 func (a *App) GetThreadsForUser(userID, teamID string, options model.GetUserThreadsOpts) (*model.Threads, *model.AppError) {
 	var result model.Threads
 	var eg errgroup.Group
+	postPriorityIsEnabled := a.isPostPriorityEnabled()
+	if postPriorityIsEnabled {
+		options.IncludeIsUrgent = true
+	}
 
 	if !options.ThreadsOnly {
 		eg.Go(func() error {
@@ -2427,6 +2431,18 @@ func (a *App) GetThreadsForUser(userID, teamID string, options model.GetUserThre
 
 			return nil
 		})
+
+		if postPriorityIsEnabled {
+			eg.Go(func() error {
+				totalUnreadUrgentMentions, err := a.Srv().Store().Thread().GetTotalUnreadUrgentMentions(userID, teamID, options)
+				if err != nil {
+					return errors.Wrapf(err, "failed to count urgent mentioned threads for user id=%s", userID)
+				}
+				result.TotalUnreadUrgentMentions = totalUnreadUrgentMentions
+
+				return nil
+			})
+		}
 	}
 
 	if !options.TotalsOnly {
@@ -2469,7 +2485,7 @@ func (a *App) GetThreadMembershipForUser(userId, threadId string) (*model.Thread
 }
 
 func (a *App) GetThreadForUser(threadMembership *model.ThreadMembership, extended bool) (*model.ThreadResponse, *model.AppError) {
-	thread, err := a.Srv().Store().Thread().GetThreadForUser(threadMembership, extended)
+	thread, err := a.Srv().Store().Thread().GetThreadForUser(threadMembership, extended, a.isPostPriorityEnabled())
 	if err != nil {
 		return nil, model.NewAppError("GetThreadForUser", "app.user.get_threads_for_user.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
 	}
@@ -2551,7 +2567,7 @@ func (a *App) UpdateThreadFollowForUserFromChannelAdd(c request.CTX, userID, tea
 	}
 
 	message := model.NewWebSocketEvent(model.WebsocketEventThreadUpdated, teamID, "", userID, nil, "")
-	userThread, err := a.Srv().Store().Thread().GetThreadForUser(tm, true)
+	userThread, err := a.Srv().Store().Thread().GetThreadForUser(tm, true, a.isPostPriorityEnabled())
 
 	if err != nil {
 		var errNotFound *store.ErrNotFound