docs: public HttpURLConnection buildConnection(URI baseServiceUri, String tail) {
      try {
        HttpURLConnection client = (HttpURLConnection) baseServiceUri.resolve(tail).toURL().openConnection();
        return client;
      } catch(MalformedURLException mue) {
        throw new EFhirClientException("Invalid Service URL", mue);
      } catch(IOException ioe) {
        throw new EFhirClientException("Unable to establish connection to server: " + baseServiceUri.toString() + tail, ioe);
      }
    }