Fixed updating mention keys when a user's username changes (#2774)

store/sql_user_store.go

@@ -141,14 +141,7 @@ func (us SqlUserStore) Update(user *model.User, allowActiveUpdate bool) StoreCha
 			}
 
 			if user.Username != oldUser.Username {
-				nonUsernameKeys := []string{}
-				splitKeys := strings.Split(user.NotifyProps["mention_keys"], ",")
-				for _, key := range splitKeys {
-					if key != oldUser.Username && key != "@"+oldUser.Username {
-						nonUsernameKeys = append(nonUsernameKeys, key)
-					}
-				}
-				user.NotifyProps["mention_keys"] = strings.Join(nonUsernameKeys, ",") + "," + user.Username + ",@" + user.Username
+				user.UpdateMentionKeysFromUsername(oldUser.Username)
 			}
 
 			if count, err := us.GetMaster().Update(user); err != nil {