private static ContentPreviewer contentPreviewer() {
        return new ContentPreviewer() {

            private HttpData data;

            @Override
            public void onData(HttpData data) {
                this.data = data;
            }

            @Override
            public String produce() {
                return data.toStringUtf8();
            }
        };
    }
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