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());
    }
Returns an {@link HttpData} which holds a SSO form.
saml/src/main/java/com/linecorp/armeria/server/saml/HttpPostBindingUtil.java