@Override
        public void onNext(HttpObject httpObject) {
            if (httpObject instanceof HttpData) {
                subscription.cancel();
            }
        }
Unlike {@link #contentPreviewBeforeEncoding()}, the content preview of this test is encoded data
because the previewing decorator is inserted after {@link EncodingService}.
core/src/test/java/com/linecorp/armeria/server/logging/ContentPreviewingServiceTest.java