docs: protected String getRequestedService(final HttpServletRequest request) {
          val targetService = request.getParameter(CasProtocolConstants.PARAMETER_TARGET_SERVICE);
          val service = request.getParameter(CasProtocolConstants.PARAMETER_SERVICE);
          val serviceAttribute = request.getAttribute(CasProtocolConstants.PARAMETER_SERVICE);
  
          if (StringUtils.isNotBlank(targetService)) {
              return targetService;
          }
          if (StringUtils.isNotBlank(service)) {
              return service;
          }
          if (serviceAttribute != null) {
              if (serviceAttribute instanceof Service) {
                  return ((Service) serviceAttribute).getId();
              }
              return serviceAttribute.toString();
          }
          return null;
      }