private static final Logger logger = LogManager.getLogger(OpenIdConnectAuthenticator.class);

    private static final BaseEncoding BASE64_DECODER = BaseEncoding.base64().withSeparator("\n", 64);

    private static final BaseEncoding BASE64URL_DECODER = BaseEncoding.base64Url().withSeparator("\n", 64);

    /** Configuration key for OpenID Connect authorization server URL. */
    protected static final String OIC_AUTH_SERVER_URL = "oic.auth.server.url";