code: function customHash(req, body) {
    const hash = crypto.createHash('md5');
  
    updateHash(hash, req);
    hash.write(body);
  
    return hash.digest('hex');
  }
docs: Creates a custom hash used as the snapshot's filename.
  @param {http.ClientRequest} req
  @param {Object} body
  @returns {String} hashed filename