def callback(self, request, **kwargs):
        """
            Called from the Service when the user accept to activate it
            :param request: request object
            :return: callback url
            :rtype: string , path to the template
        """
        return super(ServiceTrello, self).callback(request, **kwargs)
Called from the Service when the user accept to activate it
            :param request: request object
            :return: callback url
            :rtype: string , path to the template