public WebClient webClient(Consumer<WebClientBuilder> webClientCustomizer) {
        requireNonNull(webClientCustomizer, "webClientCustomizer");
        return delegate.webClient(webClientCustomizer);
    }
Returna a newly created {@link WebClient} configured by {@link #configureWebClient(WebClientBuilder)}
and then the specified customizer.
junit4/src/main/java/com/linecorp/armeria/testing/junit4/server/ServerRule.java