static HttpResponse of(CompletionStage<? extends HttpResponse> stage) {
        requireNonNull(stage, "stage");
        final DeferredHttpResponse res = new DeferredHttpResponse();
        res.delegateWhenComplete(stage);
        return res;
    }
Creates a new HTTP response that delegates to the {@link HttpResponse} produced by the specified
{@link CompletionStage}. If the specified {@link CompletionStage} fails, the returned response will be
closed with the same cause as well.

@param stage the {@link CompletionStage} which will produce the actual {@link HttpResponse}
core/src/main/java/com/linecorp/armeria/common/HttpResponse.java