Accept int for StatefulSet maxUnavailable

[AndrewMRQuinn]

General information

The maxUnavailable field is available for StatefulSets by default as of Kubernetes v1.35, and defaults to an integer value of 1. https://kubernetes.io/blog/2025/12/17/kubernetes-v1-35-release/#maxunavailable-for-statefulsets

The StatefulSetRollingUpdate class only accepted a string value, resulting in a validation error after updating to Kubernetes v1.35.

Bug reports

After updating to Kubernetes 1.35, monitoring failed for clusters containing StatefulSets. This was running on Talos Linux 1.12, which uses standard/upstream Kubernetes.
Runing cmk --debug -vvn mycluster showed the following problem:

Agent exited with code 1: 1 validation error for StatefulSetRollingUpdate
max_unavailable
  Input should be a valid string [type=string_type, input_value=1, input_type=int]
    For further information visit https://errors.pydantic.dev/2.10/v/string_type(!!)

Inspecting StatefulSets with kubectl get statefulset mystatefulset -o yaml showed the following configuration, with maxUnavailable set to an integer value of 1. This is a default value set by Kubernetes. It was not part of the manifest file.

    updateStrategy:
      rollingUpdate:
        maxSurge: 0
        maxUnavailable: 1
      type: RollingUpdate

Proposed changes

Allow max_unavailable StatefulSetRollingUpdate to accept integer values,
The PR allows both str and int, matching the RollingUpdate class in the same file. str may not be necessary, but I can't be confident that removing it wouldn't cause problems for someone else, hence matching RollingUpdate.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[AndrewMRQuinn]

I have read the CLA Document and I hereby sign the CLA or my organization already has a signed CLA.