Restoration ID to save and restore the state of the Router.
If non-null, the Router will persist the RouterDelegate's current configuration (i.e. RouterDelegate.currentConfiguration). During state restoration, the Router informs the RouterDelegate of the previous configuration by calling RouterDelegate.setRestoredRoutePath (which by default just calls RouterDelegate.setNewRoutePath). It is the responsibility of the RouterDelegate to restore its internal state based on the provided configuration.
- RestorationManager, which explains how state restoration works in Flutter.
final String? restorationScopeId;