code: def get(self, request, *args, **kwargs):
          
          if not request.GET.get('cp'):
              return HttpResponse(_('missing cp GET param'), status=400)
          self.authorize(request, *args, **kwargs)
          return HttpResponseRedirect(self.get_redirect_url(request))
docs: redirect user to captive page
          with the social auth token in the querystring
          (which will allow the captive page to send the token to freeradius)