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/public/model/notification.go

@@ -8,9 +8,10 @@ type NotificationType string
 type NotificationReason string
 
 const (
-	NotificationStatusSuccess NotificationStatus = "success"
-	NotificationStatusError   NotificationStatus = "error"
-	NotificationStatusNotSent NotificationStatus = "not_sent"
+	NotificationStatusSuccess     NotificationStatus = "success"
+	NotificationStatusError       NotificationStatus = "error"
+	NotificationStatusNotSent     NotificationStatus = "not_sent"
+	NotificationStatusUnsupported NotificationStatus = "unsupported"
 
 	NotificationTypeAll       NotificationType = "all"
 	NotificationTypeEmail     NotificationType = "email"