PLT-4027 "Added to the channel" system messages mark the channel as Unread (#3947)

store/sql_post_store.go

@@ -73,7 +73,7 @@ func (s SqlPostStore) Save(post *model.Post) StoreChannel {
 		} else {
 			time := model.GetMillis()
 
-			if post.Type != model.POST_JOIN_LEAVE {
+			if post.Type != model.POST_JOIN_LEAVE && post.Type != model.POST_ADD_REMOVE {
 				s.GetMaster().Exec("UPDATE Channels SET LastPostAt = :LastPostAt, TotalMsgCount = TotalMsgCount + 1 WHERE Id = :ChannelId", map[string]interface{}{"LastPostAt": time, "ChannelId": post.ChannelId})
 			} else {
 				// don't update TotalMsgCount for unimportant messages so that the channel isn't marked as unread