@Override
    public Mono<Void> setComplete() {
        return !isCommitted() ? doCommit(null) : Mono.empty();
    }
Return the underlying server response.

<p><strong>Note:</strong> This is exposed mainly for internal framework
use such as WebSocket upgrades in the spring-webflux module.
spring/boot3-webflux-autoconfigure/src/main/java/com/linecorp/armeria/spring/web/reactive/AbstractServerHttpResponse.java