code: def callback(self, request, **kwargs):
          
  
          try:
              UserService.objects.filter(
                  user=request.user,
                  name=ServicesActivated.objects.get(name='ServiceWallabag')
              )
          except KeyError:
              return '/'
  
          return 'wallabag/callback.html'
docs: Called from the Service when the user accept to activate it
              :param request: request object
              :return: callback url
              :rtype: string , path to the template