AttributeError: get_full_path when running any rest_framework.test.APITestCase

Describe the bug
After upgrading from django-oauth-toolkit==1.2.0 to django-oauth-toolkit==1.3.0 every single test using from rest_framework.test import APITestCase and then calling self.client.post and the like fails with this stack trace:

Traceback (most recent call last):
  File "/src/app/.venv/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/src/app/.venv/lib/python3.6/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/src/app/.venv/lib/python3.6/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/utils/decorators.py", line 45, in _wrapper
    return bound_method(*args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/views/generic/base.py", line 97, in dispatch
    return handler(request, *args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/utils/decorators.py", line 45, in _wrapper
    return bound_method(*args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/django/views/decorators/debug.py", line 76, in sensitive_post_parameters_wrapper
    return view(request, *args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/views/base.py", line 260, in post
    url, headers, body, status = self.create_token_response(request)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/views/mixins.py", line 124, in create_token_response
    return core.create_token_response(request)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/oauth2_backends.py", line 145, in create_token_response
    headers, extra_credentials)
  File "/src/app/.venv/lib/python3.6/site-packages/oauthlib/oauth2/rfc6749/endpoints/base.py", line 116, in wrapper
    return f(endpoint, uri, *args, **kwargs)
  File "/src/app/.venv/lib/python3.6/site-packages/oauthlib/oauth2/rfc6749/endpoints/token.py", line 119, in create_token_response
    request, self.default_token_type)
  File "/src/app/.venv/lib/python3.6/site-packages/oauthlib/oauth2/rfc6749/grant_types/resource_owner_password_credentials.py", line 101, in create_token_response
    self.validate_token_request(request)
  File "/src/app/.venv/lib/python3.6/site-packages/oauthlib/oauth2/rfc6749/grant_types/resource_owner_password_credentials.py", line 184, in validate_token_request
    request.password, request.client, request):
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/oauth2_validators.py", line 611, in validate_user
    u = authenticate(request, username=username, password=password)
  File "/src/app/.venv/lib/python3.6/site-packages/django/contrib/auth/__init__.py", line 73, in authenticate
    user = backend.authenticate(request, **credentials)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/backends.py", line 17, in authenticate
    valid, r = OAuthLibCore.verify_request(request, scopes=[])
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/oauth2_backends.py", line 172, in verify_request
    uri, http_method, body, headers = self._extract_params(request)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/oauth2_backends.py", line 58, in _extract_params
    uri = self._get_escaped_full_path(request)
  File "/src/app/.venv/lib/python3.6/site-packages/oauth2_provider/oauth2_backends.py", line 34, in _get_escaped_full_path
    parsed = list(urlparse(request.get_full_path()))
  File "/src/app/.venv/lib/python3.6/site-packages/oauthlib/common.py", line 436, in __getattr__
    raise AttributeError(name)
AttributeError: get_full_path

To Reproduce

Test case:

from django.conf import settings
from django.contrib.auth.models import User
from rest_framework import status
from rest_framework.test import APITestCase


class OauthAuthenticationTest(APITestCase):
    def test_should_should_return_ok_when_valid_credentials_passed(self) -> None:
        username = "user"
        password = "pw"
        User.objects.create_user(username=username, email="test@example.com", password=password)
        response = self.client.post(
            "/api/oauth/token/",
            {
                "grant_type": "password",
                "username": username,
                "password": password,
                "client_id": settings.REACT_APP_OAUTH_CLIENT_ID,
            }
        )
        self.assertEqual(status.HTTP_200_OK, response.status_code)

Expected behavior
This test should pass, as it did with version 1.2.0.

Version
1.3.0

• I have tested with the latest published release and it's still a problem.
• I have tested with the master branch and it's still a problem.

Additional context

Using django==2.2.11 and djangorestframework==3.11.0.

[blu14x]

Just setup a new project and run into the same "AttributeError: get_full_path" when trying to get a Token

[blu14x]

I had a deeper look.

With some commited "fix", the request is being passed to the authenticate() inside oauth2_validators.validate_user().
Someone was not aware that the request is one of oauthlib.Request, not a Django Request.
Breaks everything

#643 (comment)

[n2ygk]

@dms-cat a PR with that test case above would be greatly appreciated!