static String toHtml() {
        final StringBuilder b = new StringBuilder();
        b.append("<table class=\"data-table\"><tbody>\n");
        b.append("<tr>");
        b.append("<th>Name</th>\n");
        b.append("<th>Key</th>\n");
        b.append("</tr>");
        clientApis().stream()
            .filter(apiKey -> !apiKey.messageType.latestVersionUnstable())
            .forEach(apiKey -> {
                b.append("<tr>\n");
                b.append("<td>");
                b.append("<a href=\"#The_Messages_" + apiKey.name + "\">" + apiKey.name + "</a>");
                b.append("</td>");
                b.append("<td>");
                b.append(apiKey.id);
                b.append("</td>");
                b.append("</tr>\n");
            });
        b.append("</tbody></table>\n");
        return b.toString();
    }
indicates whether the API is enabled for forwarding
clients/src/main/java/org/apache/kafka/common/protocol/ApiKeys.java