Added a new endpoint to return the last used date for a template.

The existing endpoint returned a whole notification for the last time the template was used. But this only takes into account data in the last week. This new methods allows us to be specific about when the template was last used if ever but looking into the ft_notification_status table as well.

tests/app/template_statistics/test_rest.py

@@ -1,10 +1,12 @@
 import uuid
+from datetime import datetime, timedelta
 from unittest.mock import Mock
 
 import pytest
 from freezegun import freeze_time
 
-from tests.app.db import create_notification
+from app import DATETIME_FORMAT
+from tests.app.db import create_ft_notification_status, create_notification
 
 
 def set_up_get_all_from_hash(mock_redis, side_effect):
@@ -189,3 +191,42 @@ def test_get_template_statistics_for_template_returns_empty_for_old_notification
     )
 
     assert not json_resp['data']
+
+
+def test_get_last_used_datetime_for_template(
+    admin_request, sample_template
+):
+    date_from_notification = datetime.utcnow() - timedelta(hours=2)
+    create_notification(template=sample_template, created_at=date_from_notification)
+    date_from_ft_status = (datetime.utcnow() - timedelta(days=2)).date()
+    create_ft_notification_status(bst_date=date_from_ft_status,
+                                  template=sample_template)
+
+    json_resp = admin_request.get(
+        'template_statistics.get_last_used_datetime_for_template',
+        service_id=str(sample_template.service_id),
+        template_id=sample_template.id
+    )
+    assert json_resp['last_date_used'] == date_from_notification.strftime(DATETIME_FORMAT)
+
+
+def test_get_last_used_datetime_for_template_returns_400_if_service_does_not_exist(
+    admin_request, sample_template
+):
+    admin_request.get(
+        'template_statistics.get_last_used_datetime_for_template',
+        service_id=uuid.uuid4(),
+        template_id=sample_template.id,
+        _expected_status=404
+    )
+
+
+def test_get_last_used_datetime_for_template_returns_400_if_template_does_not_exist(
+    admin_request, sample_template
+):
+    admin_request.get(
+        'template_statistics.get_last_used_datetime_for_template',
+        service_id=sample_template.service_id,
+        template_id=uuid.uuid4(),
+        _expected_status=404
+    )