code: static HttpData getSsoForm(String remoteEndpointUrl,
                                 String paramName, String paramValue,
                                 @Nullable String relayState) {
          requireNonNull(remoteEndpointUrl, "remoteEndpointUrl");
          requireNonNull(paramName, "paramName");
          requireNonNull(paramValue, "paramValue");
  
          final StringBuilder html = new StringBuilder();
          html.append(XHTML.get(0))
              .append(XHTML.get(1)).append(HTML_ESCAPER.escape(remoteEndpointUrl)).append(XHTML.get(2))
              .append(XHTML.get(3)).append(HTML_ESCAPER.escape(paramName))
              .append(XHTML.get(4)).append(HTML_ESCAPER.escape(paramValue)).append(XHTML.get(5));
  
          if (relayState != null) {
              html.append(XHTML.get(3)).append(RELAY_STATE)
                  .append(XHTML.get(4)).append(HTML_ESCAPER.escape(relayState)).append(XHTML.get(5));
          }
          html.append(XHTML.get(6));
  
          return HttpData.ofUtf8(html.toString());
      }
docs: Returns an {@link HttpData} which holds a SSO form.