code: function renderResponse(res, postUrl) {
      options.fault = options.fault || {};
  
      var fault = templates['soapFault']({
        code:         options.fault.code,
        description:  options.fault.description
      });
  
      var form = options.formTemplate ?
        interpolate(options.formTemplate) : templates[(!options.plain_form ? 'form' : 'form_el')];
  
      res.set('Content-Type', 'text/html');
      res.send(form({
        callback: postUrl,
        wctx:     options.wctx,
        wresult:  fault
      }));
    }
docs: http://docs.oasis-open.org/wsfed/federation/v1.2/os/ws-federation-1.2-spec-os.pdf