docs: def begin(request, provider):
      """
          Display authentication form. This is also the first step
          in registration. The actual login is in social_complete
          function below.
      """
      # store url to where user will be redirected
      request.session['next_url'] = request.GET.get("next") or settings.LOGIN_REDIRECT_URL
  
      # start the authentication process
      backend = get_backend(provider)
      return backend.begin(request, dict(request.REQUEST.items()))