docs: public static synchronized void setServiceEnabled(XMPPConnection connection, boolean enabled) {
          if (isServiceEnabled(connection) == enabled)
              return;
  
          if (enabled) {
              ServiceDiscoveryManager.getInstanceFor(connection).addFeature(XHTMLExtension.NAMESPACE);
          }
          else {
              ServiceDiscoveryManager.getInstanceFor(connection).removeFeature(XHTMLExtension.NAMESPACE);
          }
      }