code: public function defaultApi($apiName = null)
      {
          if (is_null($apiName)) {
              return LaravelJsonApi::$defaultApi;
          }
  
          LaravelJsonApi::defaultApi($apiName);
  
          return $apiName;
      }
docs: Set or get the default API name.
  
  @param string|null $apiName
  @return string
  @deprecated 2.0.0 setting the API name via this method will be removed (getter will remain).