code: public boolean isValid(HttpServletRequest request, CaptchaRequest captcha) {
      String challenge = captcha.getRecaptcha_challenge_field();
      String response = captcha.getRecaptcha_response_field();    
      return isValid(request, challenge, response);
    }
docs: Validates the captcha response.
  
  @param request
  @param captcha
  @return