🌱 KCP: Set MinItems=1 on ExternalEtcd.Endpoints

[sbueringer]

What this PR does / why we need it:
ExternalEtcd.Endpoints is actually a required field, so an empty array should not be valid

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Follow-up to #12402

[sbueringer]

/assign @fabriziopandini @JoelSpeed

[JoelSpeed]

How confident are we that there won't be any existing clusters out there with this list empty? What happens today if the list is empty?

[sbueringer]

How confident are we that there won't be any existing clusters out there with this list empty? What happens today if the list is empty?

Local and external etcd are mutually exclusive (xref:

cluster-api/controlplane/kubeadm/internal/webhooks/kubeadm_control_plane.go

Line 530 in 1efdb87

"cannot have both external and local etcd",

). So if external etcd is configured I"m not sure how Kubernetes would work without etcd endpoints

[fabriziopandini]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: a0ff274437e4fcb7a1c4729b3d58070e2ad7cade

[JoelSpeed]

So if external etcd is configured I"m not sure how Kubernetes would work without etcd endpoints

Makes sense to me

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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