notifications: use an explicit FK mark when creating notifications, previous way was prone to cache problems.

rhodecode/apps/my_account/tests/test_my_account_notifications.py

@@ -155,6 +155,7 b' class TestNotificationsController(TestCo'
         notification = NotificationModel().create(
             created_by=cur_user, notification_subject=subject,
             notification_body=notif_body, recipients=[cur_user, u1, u2])
+        Session().commit()
 
         response = self.app.get(
             route_path('notifications_show',

rhodecode/model/db.py

@@ -3909,16 +3909,18 b' class Notification(Base, BaseModel):'
         notification.type_ = type_
         notification.created_on = datetime.datetime.now()
 
+        # For each recipient link the created notification to his account
         for u in recipients:
             assoc = UserNotification()
+            assoc.user_id = u.user_id
             assoc.notification = notification
 
             # if created_by is inside recipients mark his notification
             # as read
             if u.user_id == created_by.user_id:
                 assoc.read = True
-
-            u.notifications.append(assoc)
+            Session().add(assoc)
+
         Session().add(notification)
 
         return notification