Register the Notification model to Django admin (#4186)

src/oscar/apps/communication/admin.py

 
 from oscar.core.loading import get_model
 
-CommunicationEventType = get_model("communication", "CommunicationEventType")
 Email = get_model("communication", "Email")
-
+Notification = get_model("communication", "Notification")
+CommunicationEventType = get_model("communication", "CommunicationEventType")
 
 admin.site.register(Email)
+admin.site.register(Notification)
 admin.site.register(CommunicationEventType)