docs: @Override
      protected Event doExecute(final RequestContext context) {
          try {
              val request = WebUtils.getHttpServletRequestFromExternalWebflowContext(context);
              val wa = request.getParameter(WA);
              if (StringUtils.isNotBlank(wa) && wa.equalsIgnoreCase(WSIGNIN)) {
                  wsFederationResponseValidator.validateWsFederationAuthenticationRequest(context);
                  return super.doExecute(context);
              }
              return wsFederationRequestBuilder.buildAuthenticationRequestEvent(context);
          } catch (final Exception ex) {
              LOGGER.error(ex.getMessage(), ex);
              throw new UnauthorizedServiceException(UnauthorizedServiceException.CODE_UNAUTHZ_SERVICE, ex.getMessage());
          }
      }