Test App and E2E tests

[dopry]

Is your feature request related to a problem? Please describe.
When reviewing PRs. there is no easy way to facilitate end-to-end testing for maintainers. It would be nice if there were a Test IDP app along with Test Clients for easily validating the functionality of OAuthToolkit from an end user perspective. In addition it would provide a reference implementation for consumers of the toolkit to guide their own implementations.

Describe the solution you'd like

1. There should be example implementations in the test folder that can be used by maintainers and e2e tests.

   • /tests/apps/idp - an implementation of an IDP using django-oauth-toolkit.
   • /tests/apps/rp - an implementation of a relying party that demonstrates the available authorization flows. (authorization code, implicit, resource owner, client credentials, OpenID connect hybrid)

2. There should be a collection of playwright e2e tests that exercise each authorization flow covering login and logout scenarios.

   • /tests/e2e/test_authorization_code.py
   • /tests/e2e/test_implicit.py
   • /tests/e2e/test_resource_owner.py -
   • /tests/e2e/test_client_credentials.py
   • /tests/e2e/test_hybrid.py