[Feature] Support cross-namespace clusterclasses in cluster creation

[mantis-toboggan-md]

Turtles will soon support the use of cluster classes in different namespaces than the cluster to be provisioned. The UI needs to be updated to support a new field during cluster creation: classNamespace. If no class namespace is selected, the default is to use the same namespace as the cluster.

[Danil-Grigorev]

kubernetes-sigs/cluster-api#5673 is fixed, this will be added in the next turtles release with CAPI 1.9.5

[anmazzotti]

We could just have a "Cluster Namespace" in the second screen of Cluster creation. The UI currently uses the Class namespace's instead. However that will then need to be passed as classNamespace field:

apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
metadata:
  name: my-cluster
  namespace: my-namespace
spec:
  topology:
    class: azure-something
    classNamespace: my-clusterclasses

This requires CAPI core provider to be >= v1.6.5, which raises the question if we should have feature gates based on CAPI core and maybe even Turtles versions.

[gaktive]

We may need an annotation to indicate what versions of CAPI a specific version of Turtles works with since this is a big can of worms in the making as the engine changes.

[eva-vashkevich]

For now, we decided to just check the schema to see if this feature should be enabled