Make get_notifications return single notification by reference

app/v2/notifications/get_notifications.py

@@ -18,12 +18,23 @@ def get_notification_by_id(id):
 @notification_blueprint.route("", methods=['GET'])
 def get_notifications():
     _data = request.args.to_dict(flat=False)
+
+    # flat=False makes everything a list, but we only ever allow one value for "older_than"
     if 'older_than' in _data:
-        # flat=False makes everything a list, but we only ever allow one value for "older_than"
         _data['older_than'] = _data['older_than'][0]
 
+    # and client reference
+    if 'client_reference' in _data:
+        _data['client_reference'] = _data['client_reference'][0]
+
     data = validate(_data, get_notifications_request)
 
+    if data.get('client_reference'):
+        notification = notifications_dao.get_notification_by_reference(
+            str(api_user.service_id), data.get('client_reference'), key_type=None
+        )
+        return jsonify(notification.serialize()), 200
+
     paginated_notifications = notifications_dao.get_notifications_for_service(
         str(api_user.service_id),
         filter_dict=data,

app/v2/notifications/notification_schemas.py

@@ -78,6 +78,7 @@ get_notifications_request = {
     "description": "schema for query parameters allowed when getting list of notifications",
     "type": "object",
     "properties": {
+        "client_reference": {"type": "string"},
         "status": {
             "type": "array",
             "items": {

tests/app/v2/notifications/test_get_notifications.py

@@ -60,6 +60,40 @@ def test_get_notification_by_id_returns_200(
     assert json_response == expected_response
 
 
+def test_get_notification_by_reference_returns_200(client, notify_db, notify_db_session):
+    sample_notification_with_reference = create_sample_notification(
+        notify_db, notify_db_session, client_reference='some-client-reference')
+
+    auth_header = create_authorization_header(service_id=sample_notification_with_reference.service_id)
+    response = client.get(
+        path='/v2/notifications?client_reference={}'.format(sample_notification_with_reference.client_reference),
+        headers=[('Content-Type', 'application/json'), auth_header])
+
+    assert response.status_code == 200
+    assert response.headers['Content-type'] == 'application/json'
+
+
+def test_get_notification_by_reference_nonexistent_reference_returns_400(client, sample_notification):
+    auth_header = create_authorization_header(service_id=sample_notification.service_id)
+    response = client.get(
+        path='/v2/notifications?client_reference={}'.format(sample_notification.client_reference),
+        headers=[('Content-Type', 'application/json'), auth_header])
+
+    assert response.status_code == 404
+    assert response.headers['Content-type'] == 'application/json'
+
+    json_response = json.loads(response.get_data(as_text=True))
+    assert json_response == {
+        "errors": [
+            {
+                "error": "NoResultFound",
+                "message": "No result found"
+            }
+        ],
+        "status_code": 404
+    }
+
+
 def test_get_notification_by_id_nonexistent_id(client, sample_notification):
     auth_header = create_authorization_header(service_id=sample_notification.service_id)
     response = client.get(