docs: private HttpURLConnection prepareConnection(Map<String, String> extraHeaders) throws IOException {
  		
  		// create URLConnection
  		HttpURLConnection connection = (HttpURLConnection) serviceUrl.openConnection(connectionProxy);
  		connection.setConnectTimeout(connectionTimeoutMillis);
  		connection.setReadTimeout(readTimeoutMillis);
  		connection.setAllowUserInteraction(false);
  		connection.setDefaultUseCaches(false);
  		connection.setDoInput(true);
  		connection.setDoOutput(true);
  		connection.setUseCaches(false);
  		connection.setInstanceFollowRedirects(true);
  		connection.setRequestMethod("POST");
  		
  		setupSsl(connection);
  		addHeaders(extraHeaders, connection);
  		
  		return connection;
  	}