Metafield Definitions available on Order, Collection, and Customer

As of API version 2022-01, you can query for metafieldDefinitions on Order, Collection, and Customer. Previously this was only available on Product and ProductVariant.

Metafield Definitions are used to define a namespace, key, and type across all instances of a type of resource. These definitions enable Admin UI so that merchants can edit these fields in the context of each resource. You can learn more about Metafield Definitions in the Developer Docs.