Isn't the typical way to do this by using a janitor? This would typically need to be done in user space (the framework doesn't know what cleanup you want to do)

Isn't the typical way to do this by using a janitor? This would typically need to be done in user space (the framework doesn't know what cleanup you want to do), but Bevy could provide an interface for it with callbacks or whatever is more idiomatic in Rust/Bevy.