private static Registry<ConnectionSocketFactory> createRegistry(SSLConnectionSocketFactory sslSocketFactory) {
        return RegistryBuilder.<ConnectionSocketFactory>create()
                .register("https", sslSocketFactory)
                .register("http", PlainConnectionSocketFactory.getSocketFactory())
                .build();
    }
Sync HTTP client builder <em>for internal Vespa communications over http/https.</em>
Configures Vespa mTLS and handles TLS mixed mode automatically.
Custom connection managers must be configured through {@link #connectionManagerFactory(HttpClientConnectionManagerFactory)}.

@author jonmv
http-utils/src/main/java/ai/vespa/util/http/hc5/VespaHttpClientBuilder.java