docs: def form_valid(self, form):
          """
          The user has provided valid credentials (this was checked in AuthenticationForm.is_valid()). So now we
          can check the test cookie stuff and log him in.
          """
          self.check_and_delete_test_cookie()
          login(self.request, form.get_user())
          return super(LoginView, self).form_valid(form)