docs: private static Charset extractCharset(Metadata headers) {
      String contentType = headers.get(GrpcUtil.CONTENT_TYPE_KEY);
      if (contentType != null) {
        String[] split = contentType.split("charset=", 2);
        try {
          return Charset.forName(split[split.length - 1].trim());
        } catch (Exception t) {
          // Ignore and assume UTF-8
        }
      }
      return Charsets.UTF_8;
    }