@Override
    public void serviceAdded(ServiceConfig cfg) throws Exception {
        super.serviceAdded(cfg);

        if (server != null) {
            if (server != cfg.server()) {
                throw new IllegalStateException("cannot be added to more than one server");
            } else {
                return;
            }
        }

        server = cfg.server();

        // Auto-detect the primary port number and its session protocol after the server started.
        server.addListener(portConfigHolder);
    }
A decorator which initiates an authentication request to the remote identity provider if the request is
not authenticated.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlDecorator.java