docs: public Mono<Response<ConfigurationSetting>> addSetting(ConfigurationSetting setting) {
          // Validate that setting and key is not null. The key is used in the service URL so it cannot be null.
          validateSetting(setting);
  
          // This service method call is similar to setSetting except we're passing If-Not-Match = "*". If the service
          // finds any existing configuration settings, then its e-tag will match and the service will return an error.
          return service.setKey(serviceEndpoint, setting.key(), setting.label(), setting, null, getETagValue(ETAG_ANY));
      }