@Override
                public void onHeaders(Request r) {
                    if (HttpMethod.CONNECT.is(r.getMethod()))
                        r.headers(hs -> proxyHeadersCopy.forEach((k, v) -> hs.add(k, v.get())));
                }
Client implementation based on Jetty HTTP Client

@author bjorncs
vespa-feed-client/src/main/java/ai/vespa/feed/client/impl/JettyCluster.java