Messages and Change Subscriptions now have user-provided identifiers
User-provided identifiers are identifiers that are not set by the API (like the
id field is), but provided by the API user (like the
orderNumber fields). In particular the design goal of the
key field is to allow client applications to only use the
key field, and ignore the API-provided
This release progresses towards the design goal by adding the
key field among other user-provided identifiers into data structures commonly used in asynchronous processing by Subscriptions and the Messages Endpoint.