text: Title: Django signal user_logged_in is not always fired when login via login endpoint is performed successfully
  Body: ### Checklist
  
  *   [x] I read [Contribution Guidelines](https://github.com/apragacz/django-rest-registration/blob/master/CONTRIBUTING.md#issues)
  *   [x] I searched existing issues before opening this one
  *   [x] This is not a major security issue
  *   [x] I reproduced the bug with the newest version
  
  #### Optional checklist
  
  *   [ ] I attached a PR with a test case reproducing the problem
  
  ### Describe the bug
  
  This is spin-off from issue #276
  
  For session-based logins, we're using `auth.login()`:
  
  https://github.com/apragacz/django-rest-registration/blob/e6421ac9541b683dcb86e8136df39d59c0d5f3b4/rest_registration/api/views/login.py#L103
      
  which in turn fires `user_logged_in` signal:
  https://github.com/django/django/blob/5e98959d9242c57a55c65847758781f82d386fa4/django/contrib/auth/__init__.py#L152
  
  which will run connected `update_last_login` handler:
  https://github.com/django/django/blob/9c19aff7c7561e3a82978a272ecdaad40dda5c00/django/contrib/auth/apps.py#L28
  
  However, for token-based logins, we're not using `auth.login()` for obvious reasons. but we neither fire `user_logged_in` signal, which should be fired in that case.
  
  The consequence of that is `last_login` field is not updated.
  
  ### Expected behavior
  `user_logged_in` is being fired exactly once when successful login happens using the `LoginView` / `login()` API view.
  
  ### Actual behavior
  `user_logged_in` is being fired only when session-based  login happens.
  
  ### Steps to reproduce
  Steps to reproduce the behavior:
  Provide a token-only login based configuration
  
  ### Diagnostic info
  
  n/a
  
  ### Additional context
  n/a
  