docs: public static String getFirstResourceId(final CacheKey key) {
      try {
        if (key instanceof MultiCacheKey) {
          List<CacheKey> keys = ((MultiCacheKey) key).getCacheKeys();
          return secureHashKey(keys.get(0));
        } else {
          return secureHashKey(key);
        }
      } catch (UnsupportedEncodingException e) {
        // This should never happen. All VMs support UTF-8
        throw new RuntimeException(e);
      }
    }