How do Dio interceptors let you centrally add a shared authentication header to every single outgoing request, or centrally handle a genuine expired token error consistently across your entire app?

A Dio interceptor lets you properly hook into the request, response, or error lifecycle of essentially every single network call your app makes, and a genuinely common pattern uses an onRequest interceptor to automatically attach a shared authentication token header to every single outgoing request without needing to manually add it individually within every single separate API call, while a corresponding onError interceptor can properly detect a genuine expired authentication token, then automatically attempt to properly refresh that token and correctly retry the original genuinely failed request, all handled consistently in one single centralized location.

dio.interceptors.add(InterceptorsWrapper(
  onRequest: (options, handler) {
    options.headers['Authorization'] = 'Bearer $token';
    handler.next(options);
  },
));