static RestClient of(WebClient webClient) {
        requireNonNull(webClient, "webClient");

        if (webClient == WebClient.of()) {
            return of();
        }
        return new DefaultRestClient(webClient);
    }
Returns a new {@link RestClient} with the specified {@link WebClient}.
core/src/main/java/com/linecorp/armeria/client/RestClient.java