Storefront API Cart now exposes selling plan errors

As of version 2025-07 of the GraphQL Storefront API, enhanced error handling for selling plans is introduced. The Cart mutations now expose specific user errors for scenarios involving selling plans:

• VARIANT_REQUIRES_SELLING_PLAN: The error is returned when a merchandise added to the cart requires a selling plan, but none is provided.
• SELLING_PLAN_NOT_APPLICABLE: The error is returned when a selling plan is added to a merchandise in the cart but is not applicable.