Add "frameworks" to the list of audit object types
Add "frameworks" to the list of audit object types

Framework stats snapshot events are associated with a framework
object, so this adds "frameworks" to the list of object types that
can be used with audit events API endpoints.

Framework slug is used as object_id since similar to service_id it's
used to reference the framework object everywhere outside the API.

alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api