🐛 implement conversion for OpenStackClusterTemplate CRD

[apricote]

What this PR does / why we need it:

Adds Hub() methods to v1alpha5 OpenStackClusterTemplate struct and implements Convertible interface in v1alpha4. API was only introduced in v1alpha4, so conversion to/from v1alpha3 is not needed.

conversion-gen already generated the automatic conversion functions.

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 #1248

/hold

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[apricote]

This blocks upgrading to CAPO v0.6 for us and anyone else using ClusterClass in v0.5.

/cherry-pick release-0.6

[k8s-infra-cherrypick-robot]

@apricote: once the present PR merges, I will cherry-pick it on top of release-0.6 in a new PR and assign it to you.

In response to this:

This blocks upgrading to CAPO v0.6 for us and anyone else using ClusterClass in v0.5.

/cherry-pick release-0.6

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/test-infra repository.

[tobiasgiese]

/approve
/lgtm

Thanks for this fast bugfix! 👍🏻 💯

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: apricote, tobiasgiese

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• OWNERS [tobiasgiese]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[apricote]

/hold cancel

[k8s-infra-cherrypick-robot]

@apricote: new pull request created: #1250

In response to this:

This blocks upgrading to CAPO v0.6 for us and anyone else using ClusterClass in v0.5.

/cherry-pick release-0.6

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/test-infra repository.