public Mono<Void> setComplete(@Nullable Throwable cause) {
        return !isCommitted() ? doCommit(null).then(Mono.defer(() -> cleanup(cause)))
                              : Mono.defer(() -> cleanup(cause));
    }
Closes the {@link HttpResponseWriter} with the specified {@link Throwable} which is raised during
sending the response.
spring/boot3-webflux-autoconfigure/src/main/java/com/linecorp/armeria/spring/web/reactive/ArmeriaServerHttpResponse.java