Fix wrong permissions on dashboard pages

Anyone with access to a service should be able to see:
- monthly breakdown (non financial)
- incoming messages

Adds tests to check the same.

tests/conftest.py

@@ -1409,6 +1409,27 @@ def mock_get_monthly_template_statistics(mocker, service_one, fake_uuid):
     )
 
 
+@pytest.fixture(scope='function')
+def mock_get_monthly_notification_stats(mocker, service_one, fake_uuid):
+    def _stats(service_id, year):
+        return {'data': {
+            datetime.utcnow().strftime('%Y-%m'): {
+                "email": {
+                    "sending": 1,
+                    "delivered": 1,
+                },
+                "sms": {
+                    "sending": 1,
+                    "delivered": 1,
+                },
+            }
+        }}
+    return mocker.patch(
+        'app.service_api_client.get_monthly_notification_stats',
+        side_effect=_stats
+    )
+
+
 @pytest.fixture(scope='function')
 def mock_get_template_statistics_for_template(mocker, service_one):
     def _get_stats(service_id, template_id):