ensure AKS immutable configuration has webhook enforcement

[jackfrancis]

What type of PR is this?

/kind bug
/kind cleanup

What this PR does / why we need it:

This PR replaces a few, one-off validation implementations to re-use common funcs instead.

More importantly, the following AzureManagedControlPlane properties have been fixed for strict immutability as according the requirements of the AKS API for those properties:

• Spec.SSHPublicKey
• Spec.DNSServiceIP
• Spec.NetworkPlugin
• Spec.NetworkPolicy
• Spec.LoadBalancerSKU

And the following AzureManagedMachinePool properties as well:

• Spec.OSDiskSizeGB
• Spec.MaxPods
• Spec.OsDiskType

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 #

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

ensure AKS immutable configuration has webhook enforcement

[k8s-ci-robot]

@jackfrancis: The label(s) kind/fix cannot be applied, because the repository doesn't have them.

In response to this:

What type of PR is this?

/kind fix
/kind cleanup

What this PR does / why we need it:

This PR replaces a few, one-off validation implementations to re-use common funcs instead.

More importantly, the following AzureManagedControlPlane properties have been fixed for strict immutability as according the requirements of the AKS API for those properties:

• Spec.SSHPublicKey
• Spec.DNSServiceIP
• Spec.NetworkPlugin
• Spec.NetworkPolicy
• Spec.LoadBalancerSKU

And the following AzureManagedMachinePool properties as well:

• Spec.OSDiskSizeGB
• Spec.MaxPods
• Spec.OsDiskType

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 #

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

ensure AKS immutable configuration has webhook enforcement

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.

[jackfrancis]

This new func is in response to a comment from @nojnhuh here that the existing ensureStringSlicesAreEqual func has a bug (and isn't unit tested).

[mboersma]

/lgtm

Nice refactoring! This is simpler and more readable by far.

[jackfrancis]

I labeled this kind/bug because strictly speaking the subtle changes to immutability across the described properties reflect a bug in the way we're dealing with the AKS API, but I would advocate we not cherry-pick these changes.

Unless we hear from folks who are running into these edge cases in the wild.

Thoughts @mboersma @CecileRobertMichon @nojnhuh ?

[mboersma]

...I would advocate we not cherry-pick these changes.

Unless we hear from folks who are running into these edge cases in the wild.

Makes sense to me.

[jackfrancis]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

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[jackfrancis]

/retest