✨ Add OpenStackClusterIdentity for centralized credential management

[bnallapeta]

What this PR does / why we need it:
Introduces OpenStackClusterIdentity CRD to centralize OpenStack credentials across namespaces with access controls.

Key Features:

• Cluster-scoped credential storage (reduces duplication)
• Namespace-based access control via namespaceSelector
• Backward compatible with existing Secret references

Usage:

# Create cluster identity
apiVersion: infrastructure.cluster.x-k8s.io/v1alpha1
kind: OpenStackClusterIdentity
metadata:
  name: production-openstack
spec:
  secretRef:
    name: openstack-credentials
    namespace: capo-system

# Reference from cluster
spec:
  identityRef:
    type: ClusterIdentity
    name: production-openstack
    cloudName: openstack

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #2386

• squashed commits
• if necessary:
  • includes documentation
  • adds unit tests
  • adds envtest tests
  • adds e2e tests

/hold

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @bnallapeta. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[lentzi90]

/ok-to-test

[bnallapeta]

/test pull-cluster-api-provider-openstack-e2e-test

[k8s-ci-robot]

PR needs rebase.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.