private HttpResponse fail(ServiceRequestContext ctx,
                              LogoutRequest logoutRequest,
                              SamlEndpoint sloResEndpoint) {
        // Try to send a LogoutResponse with the following status code. It's one of the top-level status code
        // which is defined in SAML 2.0 specifications.
        //
        // "urn:oasis:names:tc:SAML:2.0:status:Responder"
        // - The request could not be performed due to an error on the part of the SAML responder
        //   or SAML authority.
        final LogoutResponse failureResponse = createLogoutResponse(logoutRequest, StatusCode.RESPONDER);
        try {
            return respond(failureResponse, sloResEndpoint);
        } catch (SamlException e) {
            return fail(ctx, e);
        }
    }
A service which receives a single logout request from an identity provider in order to perform a global
logout.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlSingleLogoutFunction.java