@Override
    public void connectFailed(SessionProtocol protocol, Endpoint endpoint,
                              SocketAddress socketAddress, Throwable throwable) {
        requireNonNull(protocol, "protocol");
        requireNonNull(endpoint, "endpoint");
        proxySelector.connectFailed(endpoint.toUri(protocol),
                                    requireNonNull(socketAddress, "socketAddress"),
                                    new IOException(throwable));
    }
Converts {@link SessionProtocol}, {@link Endpoint} to a uri without serialization format.
core/src/main/java/com/linecorp/armeria/client/proxy/WrappingProxyConfigSelector.java