Revert " #4755 Combining consecutive user join/leave system messages to single message and few other changes." (#7072)

* Revert "PLT-6603: Don't return all posts on invalid query. (#7061)"

This reverts commit 25a2013890.

* Revert " #4755 Combining consecutive user join/leave system messages to single message and few other changes. (#5945)"

This reverts commit 8a91235fb3.

app/notification.go

@@ -306,91 +306,6 @@ func SendNotifications(post *model.Post, team *model.Team, channel *model.Channe
 	return mentionedUsersList, nil
 }
 
-func SendNotificationsForSystemMessageAddRemove(user *model.User, otherUser *model.User, channel *model.Channel, post *model.Post) *model.AppError {
-	otherUserChannelMember, _ := GetChannelMember(channel.Id, otherUser.Id)
-	team, err := GetTeam(channel.TeamId)
-	if err != nil {
-		return err
-	}
-
-	err = (<-Srv.Store.Channel().IncrementMentionCount(channel.Id, otherUser.Id)).Err
-	if err != nil {
-		return err
-	}
-
-	if utils.Cfg.EmailSettings.SendEmailNotifications {
-		userAllowsEmails := otherUser.NotifyProps[model.EMAIL_NOTIFY_PROP] != "false"
-		if otherUserChannelMember != nil {
-			channelEmail, ok := otherUserChannelMember.NotifyProps[model.EMAIL_NOTIFY_PROP]
-			if ok && channelEmail != model.CHANNEL_NOTIFY_DEFAULT {
-				userAllowsEmails = channelEmail != "false"
-			}
-		}
-
-		var status *model.Status
-		var err *model.AppError
-		if status, err = GetStatus(otherUser.Id); err != nil {
-			status = &model.Status{
-				UserId:         otherUser.Id,
-				Status:         model.STATUS_OFFLINE,
-				Manual:         false,
-				LastActivityAt: 0,
-				ActiveChannel:  "",
-			}
-		}
-
-		senderName := utils.T("system.message.name")
-		if userAllowsEmails && status.Status != model.STATUS_ONLINE && otherUser.DeleteAt == 0 {
-			if err = sendNotificationEmail(post, otherUser, channel, team, senderName, user); err != nil {
-				return err
-			}
-		}
-	}
-
-	if otherUserChannelMember != nil {
-		sendPushNotifications := false
-		if *utils.Cfg.EmailSettings.SendPushNotifications {
-			pushServer := *utils.Cfg.EmailSettings.PushNotificationServer
-			if pushServer == model.MHPNS && (!utils.IsLicensed || !*utils.License.Features.MHPNS) {
-				l4g.Warn(utils.T("api.post.send_notifications_and_forget.push_notification.mhpnsWarn"))
-				sendPushNotifications = false
-			} else {
-				sendPushNotifications = true
-			}
-		}
-
-		channelName := channel.DisplayName
-		senderUsername := user.Username
-
-		if sendPushNotifications {
-			var status *model.Status
-			var err *model.AppError
-			if status, err = GetStatus(otherUser.Id); err != nil {
-				status = &model.Status{UserId: otherUser.Id, Status: model.STATUS_OFFLINE, Manual: false, LastActivityAt: 0, ActiveChannel: ""}
-			}
-
-			if ShouldSendPushNotification(otherUser, otherUserChannelMember.NotifyProps, true, status, post) {
-				if err = sendPushNotification(post, otherUser, channel, senderUsername, channelName, true); err != nil {
-					return err
-				}
-			}
-		}
-
-		message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POSTED, "", post.ChannelId, "", nil)
-		message.Add("post", post.ToJson())
-		message.Add("channel_type", channel.Type)
-		message.Add("channel_display_name", channelName)
-		message.Add("channel_name", channel.Name)
-		message.Add("sender_name", senderUsername)
-		message.Add("team_id", channel.TeamId)
-		message.Add("mentions", otherUser.Username)
-
-		Publish(message)
-	}
-
-	return nil
-}
-
 func sendNotificationEmail(post *model.Post, user *model.User, channel *model.Channel, team *model.Team, senderName string, sender *model.User) *model.AppError {
 	if channel.IsGroupOrDirect() {
 		if result := <-Srv.Store.Team().GetTeamsByUserId(user.Id); result.Err != nil {