text: Title: TestClient request mock HttpRequest is missing SessionStore session attribute
  Body: **AttributeError: Mock object has no attribute 'session'**
  This error is raised when using TestClient to test a login endpoint that uses `django.contrib.auth.login` because the mock request object as defined here https://github.com/vitalik/django-ninja/blob/master/ninja/testing/client.py#L128-L138 is missing a session attribute.
  
  **Possible Solution**
   I was able to solve this issue on my own by monkey patching the test client by defining a function like 
  
  ```
  from django.contrib.sessions.backends.db import SessionStore
  def _new_build_request(self, *args, **kwargs) -> Mock:
      """Method to be monkey patched into the TestClient to add session store to the request mock"""
      mock = self._old_build_request(*args, **kwargs)
      mock.session = SessionStore()
      return mock
  ```
  and then using this new function to replace the `_build_request` function in my TestClient instance like
  ```
  client._old_build_request = client._build_request
  client._build_request = _new_build_request.__get__(client)
  ```
  
  Maybe a  better solution would be to use a SessionStore mock?