code: func (client *Client) UpdateRouteApplication(routeGUID string, appGUID string) (Route, Warnings, error) {
  	request, err := client.newHTTPRequest(requestOptions{
  		RequestName: internal.PutRouteAppRequest,
  		URIParams: map[string]string{
  			"app_guid":   appGUID,
  			"route_guid": routeGUID,
  		},
  	})
  	if err != nil {
  		return Route{}, nil, err
  	}
  
  	var route Route
  	response := cloudcontroller.Response{
  		DecodeJSONResponseInto: &route,
  	}
  	err = client.connection.Make(request, &response)
  
  	return route, response.Warnings, err
  }
docs: // UpdateRouteApplication creates a link between the route and application.