controller add CozystackResourceDefinition reconciler (#1313)

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## What this PR does


### Release note

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```release-note
- add cozystackresource reconciler
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Introduced automated rolling restarts for the "cozystack-api"
deployment in the "cozy-system" namespace when changes are detected in
related custom resources. This ensures updates are applied smoothly
without manual intervention.
* Added debounce logic to optimize restart frequency, preventing
multiple rapid restarts by consolidating events within a configurable
time window.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

cmd/cozystack-controller/main.go

@@ -206,6 +206,14 @@ func main() {
 		os.Exit(1)
 	}
 
+	if err = (&controller.CozystackResourceDefinitionReconciler{
+		Client: mgr.GetClient(),
+		Scheme: mgr.GetScheme(),
+	}).SetupWithManager(mgr); err != nil {
+		setupLog.Error(err, "unable to create controller", "controller", "CozystackResourceDefinitionReconciler")
+		os.Exit(1)
+	}
+
 	// +kubebuilder:scaffold:builder
 
 	if err := mgr.AddHealthzCheck("healthz", healthz.Ping); err != nil {

internal/controller/cozystackresource_controller.go

@@ -0,0 +1,117 @@
+package controller
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	cozyv1alpha1 "github.com/cozystack/cozystack/api/v1alpha1"
+	appsv1 "k8s.io/api/apps/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/handler"
+	"sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/reconcile"
+)
+
+type CozystackResourceDefinitionReconciler struct {
+	client.Client
+	Scheme *runtime.Scheme
+
+	// Configurable debounce duration
+	Debounce time.Duration
+
+	// Internal state for debouncing
+	mu          sync.Mutex
+	lastEvent   time.Time // Time of last CRUD event on CozystackResourceDefinition
+	lastHandled time.Time // Last time the Deployment was actually restarted
+}
+
+// Reconcile handles the logic to restart the target Deployment only once,
+// even if multiple events occur close together
+func (r *CozystackResourceDefinitionReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
+	log := log.FromContext(ctx)
+
+	// Only respond to our target deployment
+	if req.Namespace != "cozy-system" || req.Name != "cozystack-api" {
+		return ctrl.Result{}, nil
+	}
+
+	r.mu.Lock()
+	le := r.lastEvent
+	lh := r.lastHandled
+	debounce := r.Debounce
+	r.mu.Unlock()
+
+	if debounce <= 0 {
+		debounce = 5 * time.Second
+	}
+
+	// No events received yet — nothing to do
+	if le.IsZero() {
+		return ctrl.Result{}, nil
+	}
+
+	// Wait until the debounce duration has passed since the last event
+	if d := time.Since(le); d < debounce {
+		return ctrl.Result{RequeueAfter: debounce - d}, nil
+	}
+
+	// Already handled this event — skip restart
+	if !lh.Before(le) {
+		return ctrl.Result{}, nil
+	}
+
+	// Perform the restart by patching the deployment annotation
+	deploy := &appsv1.Deployment{}
+	if err := r.Get(ctx, types.NamespacedName{Namespace: "cozy-system", Name: "cozystack-api"}, deploy); err != nil {
+		log.Error(err, "Failed to get Deployment cozy-system/cozystack-api")
+		return ctrl.Result{}, client.IgnoreNotFound(err)
+	}
+
+	patch := client.MergeFrom(deploy.DeepCopy())
+	if deploy.Spec.Template.Annotations == nil {
+		deploy.Spec.Template.Annotations = make(map[string]string)
+	}
+	deploy.Spec.Template.Annotations["kubectl.kubernetes.io/restartedAt"] = time.Now().Format(time.RFC3339)
+
+	if err := r.Patch(ctx, deploy, patch); err != nil {
+		log.Error(err, "Failed to patch Deployment annotation")
+		return ctrl.Result{}, err
+	}
+
+	// Mark this event as handled
+	r.mu.Lock()
+	r.lastHandled = le
+	r.mu.Unlock()
+
+	log.Info("Deployment cozy-system/cozystack-api successfully restarted")
+	return ctrl.Result{}, nil
+}
+
+// SetupWithManager configures how the controller listens to events
+func (r *CozystackResourceDefinitionReconciler) SetupWithManager(mgr ctrl.Manager) error {
+	if r.Debounce == 0 {
+		r.Debounce = 5 * time.Second
+	}
+
+	return ctrl.NewControllerManagedBy(mgr).
+		Named("cozystack-restart-controller").
+		Watches(
+			&cozyv1alpha1.CozystackResourceDefinition{},
+			handler.EnqueueRequestsFromMapFunc(func(ctx context.Context, obj client.Object) []reconcile.Request {
+				r.mu.Lock()
+				r.lastEvent = time.Now()
+				r.mu.Unlock()
+				return []reconcile.Request{{
+					NamespacedName: types.NamespacedName{
+						Namespace: "cozy-system",
+						Name:      "cozystack-api",
+					},
+				}}
+			}),
+		).
+		Complete(r)
+}