Dispose callback for when an AutoDisposeNotifier is disposed

[Colton127]

In Notifier's, ref.onDispose executes whenever the build method is called. However, the Notifier itself isn't rebuilt. Ref.onCancel has the following warning: "When the callback is invoked, there is no guarantee that the provider will get paused/dispose. It is possible that after the last listener is removed, a new listener is immediately added."

Is there a callback that is executed when a Notifier itself is disposed? In StateNotifier, this could be accomplished via overriding dispose, but that doesn't seem to be an option in Notifiers.

Thank you