code: function validateRequest(authToken, twilioHeader, url, params) {
    var expectedSignature = getExpectedTwilioSignature(authToken, url, params);
    return scmp(Buffer.from(twilioHeader), Buffer.from(expectedSignature));
  }
docs: Utility function to validate an incoming request is indeed from Twilio
  
  @param {string} authToken - The auth token, as seen in the Twilio portal
  @param {string} twilioHeader - The value of the X-Twilio-Signature header from the request
  @param {string} url - The full URL (with query string) you configured to handle this request
  @param {object} params - the parameters sent with this request
  @returns {boolean} - valid