Support for custom sub-resources

[nikhilk]

Does (or more likely, could) metacontroller support building custom sub-resources?

Context:
https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/#advanced-features-and-flexibility -- the doc mentions examples of "log" and "exec" as non-CRUD operations that could be accomplished via custom sub-resources and API aggregation.

Example use-case:
Given a CRD for creating/managing backups, it would be interesting to model restore as a custom sub-resource, so it is tied to a backup instance (or alternatively, as a custom sub-resource on the CRD representing the instance being restored).

Backup:
/api/v1/namespaces/ns/backups/backup-name

Restore:
/api/v1/namespaces/ns/backups/backup-name/restore