Process config contents with cdrouter-cli -upgrade-config.

        :param contents: Config contents as string.
        :return: :class:`configs.UpgradeConfig <configs.UpgradeConfig>` object
        :rtype: configs.UpgradeConfig

def upgrade_config(self, contents):
        """Process config contents with cdrouter-cli -upgrade-config.

        :param contents: Config contents as string.
        :return: :class:`configs.UpgradeConfig <configs.UpgradeConfig>` object
        :rtype: configs.UpgradeConfig
        """
        schema = UpgradeConfigSchema()
        resp = self.service.post(self.base,
                                 params={'process': 'upgrade'}, json={'contents': contents})
        return self.service.decode(schema, resp)