In the effort to reduce the number of database connections I introduced a small bug. This only affected the test templated letter flow, a None type error would happen when trying to creathe completed_at timestamp for a delivered message.

In the previous PR I removed the `update_notification` method to reduce the need for another update query. However, that meant the notification was marked as delivered without an updated_at timestamp.

It is weird to set the updated_at when we create the notification. So is this a better fix? Or do I put the update back now?

I recommend we push this fix now.

tests/app/v2/notifications/test_post_letter_notifications.py

@@ -245,6 +245,7 @@ def test_post_letter_notification_with_test_key_creates_pdf_and_sets_status_to_d
     fake_create_letter_task.assert_called_once_with([str(notification.id)], queue='research-mode-tasks')
     assert not fake_create_dvla_response_task.called
     assert notification.status == NOTIFICATION_DELIVERED
+    assert notification.updated_at is not None
 
 
 @pytest.mark.parametrize('env', [