@Override
        public void init() throws IOException {
            if (count.incrementAndGet() == 1)
                delegate.init();
        }
<code>RefCountingVerificationKeyResolver</code> allows us to share a single
{@link CloseableVerificationKeyResolver} instance between multiple
{@link AuthenticateCallbackHandler} instances and perform the lifecycle methods the
appropriate number of times.
clients/src/main/java/org/apache/kafka/common/security/oauthbearer/OAuthBearerValidatorCallbackHandler.java