MM-7188: Cleaning push notification on every read, not only on channel switch (#9348)

* MM-7188: Cleaning push notification on every read, not only on channel switch

* Removed unnecesary goroutine

* Fixing tests

* Applying suggestion from PR

store/sqlstore/user_store.go

@@ -949,6 +949,16 @@ func (us SqlUserStore) GetUnreadCountForChannel(userId string, channelId string)
 	})
 }
 
+func (us SqlUserStore) GetAnyUnreadPostCountForChannel(userId string, channelId string) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		if count, err := us.GetReplica().SelectInt("SELECT SUM(c.TotalMsgCount - cm.MsgCount) FROM Channels c INNER JOIN ChannelMembers cm ON c.Id = :ChannelId AND cm.ChannelId = :ChannelId AND cm.UserId = :UserId", map[string]interface{}{"ChannelId": channelId, "UserId": userId}); err != nil {
+			result.Err = model.NewAppError("SqlUserStore.GetMentionCountForChannel", "store.sql_user.get_unread_count_for_channel.app_error", nil, err.Error(), http.StatusInternalServerError)
+		} else {
+			result.Data = count
+		}
+	})
+}
+
 func (us SqlUserStore) Search(teamId string, term string, options map[string]bool) store.StoreChannel {
 	return store.Do(func(result *store.StoreResult) {
 		searchQuery := ""