code: public void addConnectionRequestProxyListener(ConnectRequestProxyListener listener) {
          if (listener == null) {
              throw new IllegalArgumentException("Parameter listener must not be null.");
          }
  
          if (connectRequestProxyListeners == null) {
              connectRequestProxyListeners = new ArrayList<>();
          }
          connectRequestProxyListeners.add(listener);
      }
docs: Adds the given {@link ConnectRequestProxyListener} to the extension hook, to be later notified of CONNECT requests
  received by the local proxy.
  <p>
  By default, the {@code ConnectRequestProxyListener}s added are removed from the local proxy when the extension is
  unloaded.
  
  @param listener the {@code ConnectRequestProxyListener} that will be added and then notified
  @throws IllegalArgumentException if the given {@code listener} is {@code null}.
  @since 2.5.0