AuthorizationServiceConfiguration.fromUrl support

I am building a AppAuth service similar to #407 and i would like to have the option to use the fetchFromUrl() with the discovery url to load my service config as part of the service initialization, before atempting to log in with the service.

I saw the Android AppAuth library offers a fetchFromUrl function for the AuthorizationServiceConfiguration so maybe there could be option to add it here as well.

final FlutterAppAuth _appAuth = FlutterAppAuth();
Completer<void> oidcInitCompleter = Completer<void>();
late final String _clientId;
late final String _discoveryUrl;
late final String _redirectUrl;
AuthorizationServiceConfiguration? _serviceConfiguration;

AppAuthService() {
    _discoveryUrl = someDiscoveryURI;
    _clientId = someClientID;
    _redirectUrl = "someURI;
    /*  Wanted Feature:
   _serviceConfiguration = await  _appAuth.fetchFromUrl(_discoveryUrl);
   */
   oidcInitCompleter.future.then((value) => notifyListeners())
}