chore: change v2alpha1 SubNamespace status to kstatus-compatible subresource

[erikgb]

A new and currently unserved API version was added with #101. This PR makes status in the new version a subresource compatible with kstatus.

I have also added conversion code with unit tests, so you can get an idea of how I plan to move forward after this is (hopefully) merged. The next steps will probably be:

1. Add conversion webhook using the conversion logic established in this PR.
2. Make v2alpha1 served, migrate controller to reconcile v2alpha1 and make v2alpha1 the storage version.

I would prefer using SSA when updating status from controller in the latter step. Please let me know what you think! This is probably best done by generating apply-configurations in a separate pre-PR.

Relates to #85

NOTE: The proposed fuzz conversion tests added in this PR are highly inspired by the equivalent test setup in https://github.com/kubernetes-sigs/cluster-api. Example: https://github.com/kubernetes-sigs/cluster-api/blob/main/api/v1alpha4/conversion_test.go

[erikgb]

If you want, I can split this PR:

1. Establish the new API version as a copy of v1
2. Make the new version compatible with kstatus

[erikgb]

I have now created a dedicated PR for (just) introducing the new API version: #101

[erikgb]

@zoetrope @ymmt2005 I think this PR is ready for a round of review now. Please let me know what you think!

[zoetrope]

Thank you for the excellent pull request!
I believe the PR looks great.

I wasn't familiar with the "kstatus" library before, but it looks interesting.
In situations like this, I often use apimachinery's Condition.

[erikgb]

Thank you for the excellent pull request! I believe the PR looks great.

I wasn't familiar with the "kstatus" library before, but it looks interesting. In situations like this, I often use apimachinery's Condition.

Thanks for the nice feedback, @zoetrope! We are also heavy users of apimachinery's Condition in our operators not yet migrated to SSA. I think the utilities in this package are mostly useful with CSA. But we will get to that in the follow-up PRs. 😉

[erikgb]

Is there anything more needed to get this merged?