Scaffold kea-operator: CRDs, controllers, config rendering, REST API, CI

Replace the ISC dhcpd PXE-boot VM with a Kea DHCP Kubernetes operator, modelled
on bind-operator. The operator renders kea-dhcp4 config from CRs and runs an HA
pair of kea-dhcp4 + kea-ctrl-agent servers behind an anycast Service.

- add KeaCluster/KeaSubnet/KeaClientClass/KeaAPI CRDs (group kea.unkin.net)
- render deterministic kea-dhcp4.conf + kea-ctrl-agent.conf into a ConfigMap and
  roll the StatefulSet via a config-hash annotation; best-effort hot-reload via
  the kea-ctrl-agent REST channel
- run HA hot-standby (memfile leases) with stable per-peer DNS identity from a
  StatefulSet; expose an anycast LoadBalancer Service for PureLB
- represent the full legacy dhcpd config: 198.18.13-17.0/24 pools, pool-less
  198.18.25.0/24, and the Legacy/UEFI-64 PXE arch classes (option 93)
- add the KeaAPI-spawned REST service: Terraform-friendly CRUD over subnet and
  client-class CRs (stable IDs, PUT upsert, 404 drift, bearer-token auth)
- add Makefile (patch/minor/major tag targets), distroless operator/api images,
  an AlmaLinux+EPEL kea workload image, and woodpecker CI with k8s resources +
  serviceAccountName on every step
- unit tests for config rendering, controller reconcile/config-hash, and the API

Claude-Session: https://claude.ai/code/session_01JUoARVdmhxKQHyyyp1pxeT

internal/controller/keasubnet_controller.go

@@ -0,0 +1,72 @@
+package controller
+
+import (
+	"context"
+	"fmt"
+	"net"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	v1alpha1 "git.unkin.net/unkin/kea-operator/api/v1alpha1"
+)
+
+// KeaSubnetReconciler validates KeaSubnet CRs and maintains their status. The
+// actual kea config is rendered by the KeaCluster controller, which watches
+// subnets and re-renders on change.
+type KeaSubnetReconciler struct {
+	client.Client
+	Scheme *runtime.Scheme
+}
+
+// +kubebuilder:rbac:groups=kea.unkin.net,resources=keasubnets,verbs=get;list;watch;create;update;patch;delete
+// +kubebuilder:rbac:groups=kea.unkin.net,resources=keasubnets/status,verbs=get;update;patch
+
+func (r *KeaSubnetReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
+	var subnet v1alpha1.KeaSubnet
+	if err := r.Get(ctx, req.NamespacedName, &subnet); err != nil {
+		return ctrl.Result{}, client.IgnoreNotFound(err)
+	}
+
+	if _, _, err := net.ParseCIDR(subnet.Spec.Subnet); err != nil {
+		subnet.Status.Phase = "Invalid"
+		setReady(&subnet.Status.Conditions, subnet.Generation, false, "InvalidCIDR", err.Error())
+		_ = r.Status().Update(ctx, &subnet)
+		return ctrl.Result{}, nil
+	}
+	for _, p := range subnet.Spec.Pools {
+		if err := validatePool(p); err != nil {
+			subnet.Status.Phase = "Invalid"
+			setReady(&subnet.Status.Conditions, subnet.Generation, false, "InvalidPool", err.Error())
+			_ = r.Status().Update(ctx, &subnet)
+			return ctrl.Result{}, nil
+		}
+	}
+
+	subnet.Status.Phase = "Ready"
+	subnet.Status.AssignedID = subnet.Spec.ID
+	subnet.Status.ObservedGeneration = subnet.Generation
+	setReady(&subnet.Status.Conditions, subnet.Generation, true, "Validated", "subnet accepted")
+	if err := r.Status().Update(ctx, &subnet); err != nil {
+		return ctrl.Result{}, err
+	}
+	return ctrl.Result{}, nil
+}
+
+func validatePool(p string) error {
+	// Accept "start - end" (with or without spaces) or a single address.
+	fields := splitPool(p)
+	for _, f := range fields {
+		if net.ParseIP(f) == nil {
+			return fmt.Errorf("invalid pool address %q in %q", f, p)
+		}
+	}
+	return nil
+}
+
+func (r *KeaSubnetReconciler) SetupWithManager(mgr ctrl.Manager) error {
+	return ctrl.NewControllerManagedBy(mgr).
+		For(&v1alpha1.KeaSubnet{}).
+		Complete(r)
+}