async function setForLocalService(req, res) {
    const userId = req.body.userRelated ? req.user.id : null;
    const service = await gladys.service.getLocalServiceByName(req.params.service_name);
    const variable = await gladys.variable.setValue(req.params.variable_key, req.body.value, service.id, userId);
    res.json(variable);
  }
@api {post} /api/service/:service_name/variable/:variable_key Save service variable
@apiName SaveVariable
@apiGroup Variable
@apiParam {string} value value to save