refactor: use util validation instead of hard coded regexp

Author: vknabel

api/v1alpha1/metalstackcluster_types_test.go

@@ -5,6 +5,7 @@ import (
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilvalidation "k8s.io/apimachinery/pkg/util/validation"
 )
 
 var _ = Describe("MetalStackCluster", func() {
@@ -17,8 +18,7 @@ var _ = Describe("MetalStackCluster", func() {
 		}
 
 		clusterID := cluster.GetClusterID()
-		// We extracted this regexp from an error message when trying to set a wrong label
-		Expect(clusterID).To(MatchRegexp("^(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?$"))
+		Expect(utilvalidation.IsValidLabelValue(clusterID)).To(BeEmpty())
 	})
 
 	It("GetClusterID is constant", func() {