Making CapacityBuffer ProvisioningStrategy a string (not enum)

[jakubin]

What type of PR is this?

/kind bug
/kind api-change

What this PR does / why we need it:

Different providers can have their own custom provisioning strategies. This field cannot be constrained by known in advance enum values.

Special notes for your reviewer:

Does this PR introduce a user-facing change?

CapacityBuffer ProvisioningStrategy is now a free string (not enum)

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

Make CapacityBuffer ProvisioningStrategy a string

[k8s-ci-robot]

Hi @jakubin. Thanks for your PR.

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[aleksandra-malinowska]

Can you briefly describe how this was tested?

Does this PR introduce a user-facing change?
NONE (only less validation on the field)

I'd say this is a user visible change - custom provisioning strategies are now allowed.

Otherwise LGTM

[aleksandra-malinowska]

/ok-to-test

[k8s-triage-robot]

This PR may require API review.

If so, when the changes are ready, complete the pre-review checklist and request an API review.

Status of requested reviews is tracked in the API Review project.

[jackfrancis]

/release-note-edit

Make CapacityBuffer ProvisioningStrategy a string

[jakubin]

Can you briefly describe how this was tested?

It was tested on GKE Cluster Autoscaler. CA reacted properly to a capacity buffer with an unsupported provisioning strategy - ignored it and didn't process.

[x13n]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jakubin, x13n

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• cluster-autoscaler/OWNERS [x13n]

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