code: public CacheKeyBuilder appendStrings(Collection<String> input)
    {
      appendItem(STRING_LIST_KEY, stringCollectionToByteArray(input, true));
      return this;
    }
docs: Add a collection of strings to the cache key.
  Strings in the collection are concatenated with a separator of '0xFF',
  and they appear in the cache key in their input order.
  
  @param input a collection of strings to be included in the cache key
  @return this instance