Use service model to look up service attributes

This is better than just keying into the JSON because it means you get
an exception straight away when looking up a key that doesn’t exist
(which via mocking you could ordinarily miss).

app/main/views/notifications.py

@@ -188,6 +188,6 @@ def download_notifications_csv(service_id):
             'Content-Disposition': 'inline; filename="{} - {} - {} report.csv"'.format(
                 format_date_numeric(datetime.now().strftime("%Y-%m-%dT%H:%M:%S.%fZ")),
                 filter_args['message_type'][0],
-                current_service['name'])
+                current_service.name)
         }
     )