Notification metrics fixes (#26854)

* Ensure your own posts are never ACKed

* Don't ACK mobile websocket notifications

* Add counter for the unsupported Desktop Apps

* Count only push messages when checking for acks

* Fix generated

* Add tests, fix comment

* Fix help string

* Check for nil session

server/channels/api4/system.go

@@ -641,7 +641,9 @@ func pushNotificationAck(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	c.App.CountNotificationAck(model.NotificationTypePush)
+	if ack.NotificationType == model.PushTypeMessage {
+		c.App.CountNotificationAck(model.NotificationTypePush)
+	}
 
 	err := c.App.SendAckToPushProxy(&ack)
 	if ack.IsIdLoaded {