docs: def get_next_redirect_url(request, redirect_field_name="next"):
      """
      Returns the next URL to redirect to, if it was explicitly passed
      via the request.
      """
      redirect_to = get_request_param(request, redirect_field_name)
      if not get_adapter(request).is_safe_url(redirect_to):
          redirect_to = None
      return redirect_to