use osutil username regex validation in cidata.

this will make the validation consistent both for lima username fallback
and then validation for cidata.

Signed-off-by: pvdvreede <[email protected]>

Author: pvdvreede

Diff for: pkg/cidata/template.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lima-vm/lima/pkg/iso9660util"
 
 	"github.com/containerd/containerd/identifiers"
+	"github.com/lima-vm/lima/pkg/osutil"
 	"github.com/lima-vm/lima/pkg/textutil"
 )
 
@@ -92,8 +93,8 @@ func ValidateTemplateArgs(args TemplateArgs) error {
 	if err := identifiers.Validate(args.Name); err != nil {
 		return err
 	}
-	if err := identifiers.Validate(args.User); err != nil {
-		return err
+	if !osutil.ValidateUsername(args.User) {
+		return errors.New("field User must be valid linux username")
 	}
 	if args.User == "root" {
 		return errors.New("field User must not be \"root\"")