private static Registry<ConnectionSocketFactory> createRegistry(SSLConnectionSocketFactory sslSocketFactory) {
        return RegistryBuilder.<ConnectionSocketFactory>create()
                .register("https", sslSocketFactory)
                .register("http", PlainConnectionSocketFactory.getSocketFactory())
                .build();
    }
Creates a client builder with a {@link BasicHttpClientConnectionManager} configured.
This connection manager uses a single connection for all requests. See Javadoc for details.
http-utils/src/main/java/ai/vespa/util/http/hc4/VespaHttpClientBuilder.java