xero 2-legged oauth

gistfile1.js

function test() {
  var requestURL = "https://api.xero.com/api.xro/2.0/Accounts",
      timestamp = (new Date().valueOf()/1000).toFixed(0),
      nonce = createGuid(),
      key = "consumer key from xero private app",
      publickey = "content of publickey.cer",
      requestData = {
        "method": "GET",
        "contentType": "application/xml",
        "headers": {
          "AUTHORIZATION": "OAuth realm=\"https://api.xero.com/\"," +
          "oauth_consumer_key=\"" + key + "\"," +
          "oauth_token=\"" + key + "\"," +
          "oauth_signature_method=\"" + "RSA-SHA1" + "\"," +
          "oauth_signature=\"" + publickey + "\"," +
          "oauth_timestamp=\"" + timestamp + "\"," +
          "oauth_nonce=\"" + nonce + "\"," +
          "oauth_version=\"1.0\"",
          "User-Agent": "my-private-app"
        }
      };
  
  var result = UrlFetchApp.fetch(requestURL, requestData);
  Logger.log(result.getContentText());
}

function createGuid() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
    return v.toString(16)
      });
}