Add pvca webhook

[Kostov6]

How to categorize this PR?

/area storage
/kind enhancement
/platform aws

What this PR does / why we need it:

TBD

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Release note:

[gardener-prow]

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[github-actions]

This change integrates PVC (Persistent Volume Claim) autoscaling capability into the AWS Gardener extension by adding a new dependency and implementing a webhook that automatically sets default cooldown periods for PVC autoscaler resources in shoot clusters.

Walkthrough

• New Feature: Added PVC autoscaler integration with automatic cooldown duration defaulting for volume scaling policies
• New Feature: Implemented webhook system to mutate PersistentVolumeClaimAutoscaler resources in shoot clusters
• Chore: Added pvc-autoscaler dependency to support new autoscaling functionality
• Test: Added comprehensive test coverage for the new webhook mutator functionality

The webhook ensures that when PVC autoscaler resources are created without explicit cooldown durations, they automatically receive a 6-hour default cooldown period to prevent excessive scaling operations.

_{Model: claude-sonnet-4-20250514 | Prompt Tokens: 4342 | Completion Tokens: 190}

[plkokanov]

The provider-aws extension can be installed on all types of seeds (gcp, azure, etc) depending on the required DNSRecord type and the cloud provider of the hosted shoots. We have to make sure that the aws-specific PVCA mutation does not happen in such cases.
You can check how this is done here, although I'm not sure if there's a better way to do it. For instance, the seedprovider webhook has a namespace selector that only selects shoot control plane namespaces labeled with seed.gardener.cloud/provider=aws. One thing to note is that the PVCA webhook also has to select resources from the garden namespace.

[plkokanov]

This is a webhook that runs in the seed and targets resources in the garden and shoot control plane namespaces. I think having shoot in the name is confusing and should be changed also for other occurrences in these files.

[plkokanov]

This webhook should have nothing to do with namespaces in the shoot cluster.

[plkokanov]

We always have to ensure that the CooldownDuration is at least 6 hours, meaning that if it was already set to something smaller, we should overwrite it.

[plkokanov]

Nit:

Suggested change

	var defaultCooldownDuration = &metav1.Duration{Duration: 6 * time.Hour}
	const minCooldownDuration = 6 * time.Hour

Then something like

pvca.Spec.VolumePolicies[i].ScaleUp.CooldownDuration = &metav1.Duration{Duration: minCooldownDuration}

[gardener-prow]

@plkokanov: adding LGTM is restricted to approvers and reviewers in OWNERS files.

Details

In response to this:

The provider-aws extension can be installed on all types of seeds (gcp, azure, etc) depending on the required DNSRecord type and the cloud provider of the hosted shoots. We have to make sure that the aws-specific PVCA mutation does not happen in such cases.
You can check how this is done here, although I'm not sure if there's a better way to do it. For instance, the seedprovider webhook has a namespace selector that only selects shoot control plane namespaces labeled with seed.gardener.cloud/provider=aws. One thing to note is that the PVCA webhook also has to select resources from the garden namespace.

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[gardener-prow]

PR needs rebase.

Details

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