Secrets: Add separate package for resource validation (#108097)

* Secrets: Add SecureValueService interface

* Secrets: Move resource validators to their own package/structs for reusing

pkg/registry/apis/secret/contracts/validator.go

@@ -0,0 +1,16 @@
+package contracts
+
+import (
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/apiserver/pkg/admission"
+
+	secretv1beta1 "github.com/grafana/grafana/apps/secret/pkg/apis/secret/v1beta1"
+)
+
+type SecureValueValidator interface {
+	Validate(sv *secretv1beta1.SecureValue, oldSv *secretv1beta1.SecureValue, operation admission.Operation) field.ErrorList
+}
+
+type KeeperValidator interface {
+	Validate(keeper *secretv1beta1.Keeper, oldKeeper *secretv1beta1.Keeper, operation admission.Operation) field.ErrorList
+}