Add new report to show monthly notification stats for each service

This report will be used by the engagement team. There is a form to give
a start and end date for the report, and the form is then downloaded
as a CSV file when the form is submitted.

tests/app/notify_client/test_notify_admin_api_client.py

@@ -1,4 +1,5 @@
 import uuid
+from datetime import date
 from unittest.mock import patch
 
 import pytest
@@ -6,6 +7,7 @@ import werkzeug
 
 from app.models.service import Service
 from app.notify_client import NotifyAdminAPIClient
+from app.notify_client.notification_api_client import notification_api_client
 from tests import service_json
 from tests.conftest import api_user_active, platform_admin_user, set_config
 
@@ -102,3 +104,16 @@ def test_generate_headers_sets_request_id_if_in_request_context(app_):
     }
     assert headers['X-B3-TraceId'] == request_context.request.request_id
     assert headers['X-B3-SpanId'] == request_context.request.span_id
+
+
+def test_get_notification_status_by_service(mocker):
+    mock_get = mocker.patch.object(notification_api_client, 'get')
+    start_date = date(2019, 4, 1)
+    end_date = date(2019, 4, 30)
+
+    notification_api_client.get_notification_status_by_service(start_date, end_date)
+
+    mock_get.assert_called_once_with(
+        url='service/monthly-data-by-service',
+        params={'start_date': '2019-04-01', 'end_date': '2019-04-30'}
+    )