Restoration ID to save and restore the state of the text field.
If non-null, the text field will persist and restore its current scroll offset and - if no controller has been provided - the content of the text field. If a controller has been provided, it is the responsibility of the owner of that controller to persist and restore it, e.g. by using a RestorableTextEditingController.
- RestorationManager, which explains how state restoration works in Flutter.
final String? restorationId;