How to create a dropdown dependent on another dropdown without Javascript (but using events)

[ucscode]

This can neither be described as a bug nor an issue. However, I've no better place to ask this. Consider there are 2 associate fields for user and choices.

yield AssociationField::new('user')->setQueryBuilder(...);
yield AssociationField::new('choices')->setQueryBuilder(...);

If a user is selected and the save button is clicked, then a submit event should be applied to filter only choices that belongs to the user.