HttpURLConnection open(URL url, Proxy proxy) {
    String protocol = url.getProtocol();
    OkHttpClient copy = client.clone();

    if (protocol.equals("http")) return new HttpURLConnectionImpl(url, copy);
    if (protocol.equals("https")) return new HttpsURLConnectionImpl(url, copy);
    throw new IllegalArgumentException("Unexpected protocol: " + protocol);
  }
Returns a copy of this stream handler factory that includes a shallow copy
of the internal {@linkplain OkHttpClient HTTP client}.
gateway/platforms/servlet/src/main/java/io/apiman/gateway/platforms/servlet/connectors/ok/OkUrlFactory.java