docs: public static String getSignatureBaseString(String requestMethod, String requestUrl,
        Map<String, String> protocolParameters) throws AuthException {
      StringBuilder sb = new StringBuilder();
      sb.append(requestMethod.toUpperCase()).append("&")
          .append(AuthUtils.percentEncode(normalizeUrl(requestUrl))).append("&")
          .append(AuthUtils.percentEncode(normalizeParameters(requestUrl, protocolParameters)));
      return sb.toString();
    }