Add support for the managedBy field

[mimowo]

What you would like to be added?

The support for the managedBy field which can delegate reconciliation from built-in controller, to a custom one.

The semantics of the field are:

• whenever the value is set, and it does not point to the built-in operator, then skip reconciliation
• the field is immutable
• the field is not defaulted

Why is this needed?

For context, we have in Kueue the effort (see Support Kubeflow Jobs in MultiKueue) to support kubeflow-training (it will include MPIJob), but it will not be complete without the support for managedBy.

The complete support for the users of MultiKueue (multi-cluster Kueue) means:

• simpler installation (just follow the standard installation path), otherwise only installation of MPIJob CRDs is required
• support for mixed setup in one cluster - some MPIJob could be run by MultiKueue and some by the default operator

The efforts to support the field in:

• k8s Job (alpha)
• JobSet (complete)

Love this feature?

Give it a 👍 We prioritize the features with most 👍