The custom attribute definition that contains the fields to update. This endpoint
supports sparse updates, so only new or changed fields need to be included in the request.
Only the following fields can be updated:
schema for a
Selection data type. Only changes to the named options or the maximum number of allowed
selections are supported.
For more information, see
Updatable definition fields.
To enable optimistic concurrency
control, include the optional
version field and specify the current version of the custom attribute definition.