Failure Domains

The provider publishes STACKIT availability zones as Cluster API failure domains on StackitCluster.status.failureDomains.

For a region such as eu01, the current model exposes:

eu01-1
eu01-2
eu01-3

StackitMachine.spec.availabilityZone is validated against the published failure domains when they are available. Invalid zones result in clear conditions instead of cloud API calls.

The existing single-zone templates continue to work. More advanced multi-AZ scheduling remains intentionally limited for now.

A future improvement:

Failure domains are currently derived from the configured region as <region>-1, <region>-2, and <region>-3. Production behavior should discover available STACKIT zones dynamically and publish only real failure domains.

Furthermore, Respect Machine.spec.failureDomain. The provider currently uses StackitMachine.spec.availabilityZone. For full CAPI behavior, if CAPI sets Machine.spec.failureDomain, the infrastructure machine must be placed in that failure domain. The provider should also consider surfacing the actual placement through StackitMachine.status.failureDomain.

We should document FailureDomain configuration for Controlplanes and Worker nodes.