message: Fix Express route stat reporting
  The route path can be a string, regex, or array, so it needs to be
  stringified before attempting to report it to Airbrake.
diff: @@ -2,7 +2,7 @@ import { Notifier } from '../notifier';
  export function makeMiddleware(airbrake: Notifier) {
  return function airbrakeMiddleware(req, res, next): void {
  - const route = req.route ? req.route.path : 'UNKNOWN';
  + const route = req.route?.path?.toString() ?? 'UNKNOWN';
  const metric = airbrake.routes.start(req.method, route);
  if (!metric.isRecording()) {
  next();
  @@ -11,7 +11,7 @@ export function makeMiddleware(airbrake: Notifier) {
  const origEnd = res.end;
  res.end = function abEnd() {
  - metric.route = req.route ? req.route.path : 'UNKNOWN';
  + metric.route = req.route?.path?.toString() ?? 'UNKNOWN';
  metric.statusCode = res.statusCode;
  metric.contentType = res.get('Content-Type');
  airbrake.routes.notify(metric);
  @@ -37,7 +37,9 @@ export function makeErrorHandler(airbrake: Notifier) {
  };
  if (req.route) {
  - notice.context.route = req.route.path;
  + if (req.route.path) {
  + notice.context.route = req.route.path.toString();
  + }
  if (req.route.stack && req.route.stack.length) {
  notice.context.action = req.route.stack[0].name;
  }
  