private static HttpClientBuilder createBuilder(ConnectionManagerFactory connectionManagerFactory) {
        HttpClientBuilder builder = HttpClientBuilder.create();
        addSslSocketFactory(builder, connectionManagerFactory);
        addHttpsRewritingRoutePlanner(builder);
        return builder;
    }
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