Expiry and the wallet

When a gift card expires with money still on it, that money is normally lost. With Move unused balance to the customer's wallet on expiry on (the default), it goes to a wallet instead:

1. the wallet of the customer account whose email is the recipient's email;
2. if there is none, the wallet of the buyer, when the card was bought by a signed-in shopper;
3. if neither exists, nothing moves and the admin list says why.

The customer gets an email saying the amount is now in their wallet, and they can spend it at checkout like any wallet balance. Each card's balance moves at most once; the card then shows as Used.

This needs the Digital Wallet module. While it is off, nothing moves and the list shows "turn on Digital Wallet to move it"; the balance moves on the next check (hourly) after you switch it on.