[Feature Request] Interoperability with K8S/GKE CapacityBuffer API

Is your feature request related to a problem? Please describe.

We’d like to use GKE CapacityBuffer API to dynamically over-provision API-serving Temporal workers.

K8S has a Capacity Buffer API in beta stage. GKE in particular has introduced support for active and standby capacity buffers based off this.

But there isn’t a clear way of how Temporal Worker Controller can work with these.

• The controller itself does not implement the scale subresource, so we cannot target the capacity buffer at the controller.
• The Worker Deployment Resource CRD does not yet flexible enough to support scalableRef as required by the CapacityBuffer API. Applying this per version is also probably the wrong level of abstraction.

So the workaround today is unfortunately falling back to unversioned workers on these API serving workloads.

Start by reading the GKE CapacityBuffer API requirements and tracing how the controller and Worker Deployment Resource CRD currently expose scaling. Focus on the missing scale subresource and the CRD's scalableRef support, including whether this belongs above the per-version level. Done means a documented design and working interoperability for versioned Temporal workers.