Support added for app-owned metafields

In the 2025-04 API versions of Checkout and Customer Account UI extension APIs, we've enhanced the appMetafield API to support reading app owned metafields. These metafields give you greater control over your application's data, as your app manages both the data and its visibility.

To read app-owned metafields, you must request them in your extension configuration toml file using the $app format in the namespace. This configuration makes app-owned metafields accessible through the appMetafield API in your UI extension code. Note that while you can read these metafields, writing to them is not permitted.

Currently, app-owned metafields are available in the unstable version and will be included in stable versions starting from 2025-04.

For more details, please refer to the metafield configuration guide for the Checkout UI extensions API or the Customer Account UI extensions API.