private byte[] clientInitialResponse(String authorizationId)
            throws OAuthBearerConfigException, IOException, UnsupportedCallbackException {
        return clientInitialResponse(authorizationId, false, Collections.emptyMap());
    }
If the callback handler handles the `OAuthBearerExtensionsValidatorCallback`
 and finds an invalid extension, SaslServer should throw an authentication exception
clients/src/test/java/org/apache/kafka/common/security/oauthbearer/internals/OAuthBearerSaslServerTest.java