feat(api): Add kubernetes version to coredns version mapping

[thunderboltsid]

Added script and makefile target to update coredns version mapping.
make coredns.sync will fetch the list of releases from upstream
release branches and create a mapping of k8s versions to coredns versions.

[jimmidyson]

Can you explain how this is used? The CoreDNS version mapping aren't referenced anywhere in this PR.

[thunderboltsid]

Can you explain how this is used? The CoreDNS version mapping aren't referenced anywhere in this PR.

Indeed, this PR just adds the mapping. We will need more changes to actually use that mapping (subsequent PRs). For cluster-class based clusters, we need a post cluster upgrade hook in CAREN that will set the CoreDNS version to the new version. For classic clusters, CAREN isn't in the picture, so we will need to also adopt that logic in the classic upgrade path.

[jimmidyson]

Ah OK this is for the CoreDNS upgrade issue

[dkoshkin]

Thanks for automating this!

[dlipovetsky]

Question: How do we ensure that the mapping stays up-to-date with the supported Kubernetes versions? I'm not sure that we define "supported Kubernetes versions" anywhere in the repo, actually. We also have a mapping

cluster-api-runtime-extensions-nutanix/charts/cluster-api-runtime-extensions-nutanix/values.yaml

Lines 74 to 79 in c644526

	k8sMinorVersionToCCMVersion:
	"1.27": "v1.27.9"
	"1.28": "v1.28.9"
	"1.29": "v1.29.6"
	"1.30": "v1.30.3"
	"1.31": "v1.31.0"

of versions for a different purpose.

I think we need a "source of truth" for supported Kubernetes versions, but we don't have to add it in this PR.

[dkoshkin]

Thanks for updating the semver package.

[thunderboltsid]

Question: How do we ensure that the mapping stays up-to-date with the supported Kubernetes versions? I'm not sure that we define "supported Kubernetes versions" anywhere in the repo, actually. We also have a mapping

cluster-api-runtime-extensions-nutanix/charts/cluster-api-runtime-extensions-nutanix/values.yaml

Lines 74 to 79 in c644526

	k8sMinorVersionToCCMVersion:
	"1.27": "v1.27.9"
	"1.28": "v1.28.9"
	"1.29": "v1.29.6"
	"1.30": "v1.30.3"
	"1.31": "v1.31.0"

of versions for a different purpose.
I think we need a "source of truth" for supported Kubernetes versions, but we don't have to add it in this PR.

The script in this PR looks for every version greater than a minimum version (default v1.22: 10 versions old). The source of truth is basically lookups to k/k every time this script is run (pre-commit).