fix: Improved error message for unsupported secret store kind (#4398)

Signed-off-by: Peter Swica <peter.swica@gusto.com>
Co-authored-by: Gergely Brautigam <182850+Skarlso@users.noreply.github.com>

pkg/controllers/externalsecret/externalsecret_controller.go

@@ -832,6 +832,8 @@ func shouldSkipUnmanagedStore(ctx context.Context, namespace string, r *Reconcil
 		case esv1beta1.ClusterSecretStoreKind:
 			store = &esv1beta1.ClusterSecretStore{}
 			namespace = ""
+		default:
+			return false, fmt.Errorf("unsupported secret store kind: %s", ref.Kind)
 		}
 
 		err := r.Get(ctx, types.NamespacedName{