Fired when the HTTP status line is received from the server.
- (void)onStatus:(NSString*)HTTPVersion :(int)statusCode :(NSString*)description;
func onStatus(_ HTTPVersion: String, _ statusCode: Int32, _ description: String)
HTTPVersion is a string containing the HTTP version string as returned from the server (e.g. "1.1").
StatusCode contains the HTTP status code (e.g. 200), and Description the associated message returned by the server (e.g. "OK").