pawIterateOnBodyParams-ignoreOne.js

function evaluate(context){
  var stringToSign = '';
  var request = context.getCurrentRequest();
  var bodyKeys = request.getUrlEncodedBodyKeys().sort();

  for (var i = 0; i < bodyKeys.length; i++) {
    var key = bodyKeys[i];
    if ('signature' !== key) {
      stringToSign += key + "=" + request.getUrlEncodedBodyKey(key);
    }
  }

  return stringToSign;
};