Add delete predicate for gateway class (nginxinc#1696)

Problem: The controller reconciles delete events for 
GatewayClasses that are not owned by NGF.

Solution: Add a delete function to the GatewayClass 
predicate that ignores delete events for GatewayClasses
with the wrong controller name.

internal/framework/controller/predicate/gatewayclass.go

@@ -45,3 +45,17 @@ func (gcp GatewayClassPredicate) Update(e event.UpdateEvent) bool {
 
 	return false
 }
+
+// Delete implements default DeleteEvent filter for validating a GatewayClass controllerName.
+func (gcp GatewayClassPredicate) Delete(e event.DeleteEvent) bool {
+	if e.Object == nil {
+		return false
+	}
+
+	gc, ok := e.Object.(*v1.GatewayClass)
+	if !ok {
+		return false
+	}
+
+	return string(gc.Spec.ControllerName) == gcp.ControllerName
+}

internal/framework/controller/predicate/gatewayclass_test.go

@@ -21,6 +21,7 @@ func TestGatewayClassPredicate(t *testing.T) {
 
 	g.Expect(p.Create(event.CreateEvent{Object: gc})).To(BeTrue())
 	g.Expect(p.Update(event.UpdateEvent{ObjectNew: gc})).To(BeTrue())
+	g.Expect(p.Delete(event.DeleteEvent{Object: gc})).To(BeTrue())
 
 	gc2 := &v1.GatewayClass{
 		Spec: v1.GatewayClassSpec{
@@ -31,4 +32,7 @@ func TestGatewayClassPredicate(t *testing.T) {
 	g.Expect(p.Update(event.UpdateEvent{ObjectOld: gc, ObjectNew: gc2})).To(BeTrue())
 	g.Expect(p.Update(event.UpdateEvent{ObjectOld: gc2, ObjectNew: gc})).To(BeTrue())
 	g.Expect(p.Update(event.UpdateEvent{ObjectOld: gc2, ObjectNew: gc2})).To(BeFalse())
+	g.Expect(p.Delete(event.DeleteEvent{Object: nil})).To(BeFalse())
+	g.Expect(p.Delete(event.DeleteEvent{Object: gc2})).To(BeFalse())
+	g.Expect(p.Delete(event.DeleteEvent{Object: &v1.HTTPRoute{}})).To(BeFalse())
 }