code: func (routeMapping *RouteMapping) UnmarshalJSON(data []byte) error {
  	var ccRouteMapping struct {
  		Metadata internal.Metadata `json:"metadata"`
  		Entity   struct {
  			AppGUID   string `json:"app_guid"`
  			RouteGUID string `json:"route_guid"`
  		} `json:"entity"`
  	}
  
  	err := cloudcontroller.DecodeJSON(data, &ccRouteMapping)
  	if err != nil {
  		return err
  	}
  
  	routeMapping.GUID = ccRouteMapping.Metadata.GUID
  	routeMapping.AppGUID = ccRouteMapping.Entity.AppGUID
  	routeMapping.RouteGUID = ccRouteMapping.Entity.RouteGUID
  	return nil
  }
docs: // UnmarshalJSON helps unmarshal a Cloud Controller Route Mapping