Enhancement: Upsells hide on checkouts that can't add products

Upsells and line item edit components now stay hidden on checkouts where the cart can't be changed, such as checkouts for draft order invoices.

What's new. Some checkouts, like the ones customers reach from a draft order invoice, don't allow products to be added or removed. Shoppers there used to see upsell buttons that couldn't work. Upsells now hide when products can't be added, and line item edit components hide when products can't be changed or removed. The checkout editor shows a note when this applies.

No action is needed on your end.