Restore previously used coupons

WooCommerce have made optimizations that now when the cart is empty, everything is reset. Meaning even coupons are removed, but only items removed are kept in session.

Why not coupons as well.

The idea is to cache the coupons used in session and any that are no longer used can be restored just like an item can. This feature is best with a UI to display them for customers once items are added to the cart again.