Don’t return UUID objects from the UUID convertor

Because it means you often have to cast to string in your application
code just to get your tests passing.

The method being monkey patched is originally defined here: b81aa0f18c/src/werkzeug/routing.py (L1272)

app/notify_client/invite_api_client.py

@@ -20,7 +20,7 @@ class InviteApiClient(NotifyAdminAPIClient):
                       auth_type,
                       folder_permissions):
         data = {
-            'service': str(service_id),
+            'service': service_id,
             'email_address': email_address,
             'from_user': invite_from_id,
             'permissions': ','.join(sorted(translate_permissions_from_admin_roles_to_db(permissions))),