Storefront API now returns errors when adding a gift card to a cart with missing or invalid recipient details

As of API version 2026-01, the Storefront API returns a GIFT_CARD_RECIPIENT_INVALID error when adding a gift card to a cart with missing or invalid recipient details, such as in this example.

Previously, when adding a gift card to a cart using either the cartCreate or cartLinesAdd mutations, an empty cart and empty userErrors would be returned if any of the recipient details were invalid, such as a missing email address. With this change a GIFT_CARD_RECIPIENT_INVALID error is returned for both cartCreate or cartLinesAdd mutations, so that you can use the information to surface gift card recipient errors back to the client.