@Override
    public List<String> cachedHeaders() {
        return Splitter.on(',').trimResults()
                       .omitEmptyStrings()
                       .splitToList(CACHED_HEADERS);
    }
Implementation of {@link FlagsProvider} which provides default values to {@link Flags}.
core/src/main/java/com/linecorp/armeria/common/DefaultFlagsProvider.java