[MM-60603] Don't follow threads when marking them as read on focus (#28263)

* [MM-60603] Don't follow threads when marking them as read on focus

* Fix tests

* Fix lint

* Fix the original bug in the API call

server/channels/app/user.go

@@ -2831,13 +2831,10 @@ func (a *App) UpdateThreadReadForUser(c request.CTX, currentSessionId, userID, t
 		return nil, err
 	}
 
-	opts := store.ThreadMembershipOpts{
-		Following:       true,
-		UpdateFollowing: true,
-	}
-	membership, storeErr := a.Srv().Store().Thread().MaintainMembership(userID, threadID, opts)
-	if storeErr != nil {
-		return nil, model.NewAppError("UpdateThreadReadForUser", "app.user.update_thread_read_for_user.app_error", nil, "", http.StatusInternalServerError).Wrap(storeErr)
+	// If the thread doesn't have a membership, we shouldn't try to mark it as unread
+	membership, err := a.GetThreadMembershipForUser(userID, threadID)
+	if err != nil {
+		return nil, err
 	}
 
 	previousUnreadMentions := membership.UnreadMentions