docs: function log_event(req, code, message, elapsed) {
    return {
      code:           code,
      message:        message,
      elapsed:        elapsed,
      request:        req,
      url:            req.originalUrl || req.url,
      method:         req.method,
      headers:        req.headers,
      httpVersion:    req.httpVersion,
      remoteAddress:  req.connection.remoteAddress
    };
  }