docs: @GetMapping(path = WSFederationConstants.ENDPOINT_FEDERATION_METADATA)
      public void doGet(final HttpServletRequest request, final HttpServletResponse response) throws Exception {
          try {
              response.setContentType(MediaType.TEXT_HTML_VALUE);
              val out = response.getWriter();
              val metadata = WSFederationMetadataWriter.produceMetadataDocument(casProperties);
              out.write(DOM2Writer.nodeToString(metadata));
          } catch (final Exception ex) {
              LOGGER.error("Failed to get metadata document", ex);
              response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
          }
      }