Split models to prevent circular imports

This commit is the first step to disentangling the models from the API
clients. With the models in the same folder as the API clients it makes
it hard to import the API clients within the model without getting a
circular import.

After this commit the user API clients still has this problem, but at
least the service API client doesn’t.

tests/app/notify_client/test_notify_admin_api_client.py

@@ -4,8 +4,8 @@ from unittest.mock import patch
 import pytest
 import werkzeug
 
+from app.models.service import Service
 from app.notify_client import NotifyAdminAPIClient
-from app.notify_client.models import Service
 from tests import service_json
 from tests.conftest import api_user_active, platform_admin_user, set_config
 

tests/app/notify_client/test_user_client.py

@@ -3,7 +3,7 @@ from unittest.mock import call
 import pytest
 
 from app import invite_api_client, service_api_client, user_api_client
-from app.notify_client.models import User
+from app.models.user import User
 from tests import sample_uuid
 from tests.conftest import SERVICE_ONE_ID, api_user_pending
 
@@ -51,7 +51,7 @@ def test_client_returns_count_of_users_with_manage_service(
     )
 
     mocker.patch(
-        'app.notify_client.models._get_service_id_from_view_args',
+        'app.models.user._get_service_id_from_view_args',
         return_value=SERVICE_ONE_ID,
     )
 
@@ -221,7 +221,7 @@ def test_returns_value_from_cache(
         'app.notify_client.RedisClient.set',
     )
     mock_model = mocker.patch(
-        'app.notify_client.models.User.__init__',
+        'app.models.user.User.__init__',
         return_value=None,
     )