[kenichi-mashiyama]

Summary

This PR adds support for pod anti-affinity configurations (enforcePodAntiAffinity and antiAffinity) within the Placement spec of the Instance CRD.

Motivation

Previously, the HAProxy Operator did not provide a native mechanism to configure pod anti-affinity rules for HAProxy instances. This meant users could not easily prevent multiple pods of the same instance from landing on the same node, nor could they define custom anti-affinity rules against other pod workloads or specific topology domains. By introducing enforcePodAntiAffinity (a simple toggle to ensure one pod per node) and antiAffinity (PodAntiAffinityRule for custom label-selector-based rules), users can now flexibly configure scheduling isolation to improve high availability.

Changes

• Added the EnforcePodAntiAffinity (bool) field, PodAntiAffinityRule struct, and AntiAffinity field to the Placement struct in apis/proxy/v1alpha1/instance_types.go.
• Updated reconcileStatefulSet in controllers/instance/statefulset.go to inject PodAntiAffinity terms into the StatefulSet spec when EnforcePodAntiAffinity or AntiAffinity is configured.
• Added unit tests in controllers/instance/statefulset_test.go to verify the generation of StatefulSet affinity rules for both enforcePodAntiAffinity and custom antiAffinity configurations.
• Regenerated CRDs, DeepCopy methods, and API documentation to reflect the new schema fields.

Checklist

• Code changes implemented
• Unit tests added/updated
• Generated CRDs and API docs updated

[kenichi-mashiyama]

Hi @xosk31 @m-terra,

Friendly ping when you have a chance! Could you please take a look at this PR?
All CI checks have passed. Thanks!