docs: public static String signParams(DigestAlgorithm digestAlgorithm, Map<?, ?> params, String separator, String keyValueSeparator, boolean isIgnoreNull) {
  		if (MapUtil.isEmpty(params)) {
  			return null;
  		}
  		final String paramsStr = MapUtil.join(MapUtil.sort(params), separator, keyValueSeparator, isIgnoreNull);
  		return new Digester(digestAlgorithm).digestHex(paramsStr);
  	}