fix: holder ID for userform conditional support

Author: wilr

src/KeyValueField.php

@@ -2,6 +2,7 @@
 
 namespace FullscreenInteractive\KeyValueField;
 
+use SilverStripe\Core\Convert;
 use SilverStripe\Forms\CompositeField;
 use SilverStripe\Forms\FieldList;
 use SilverStripe\Forms\LabelField;
@@ -35,6 +36,12 @@ public function setKeys(array $keys)
     }
 
 
+    public function HolderID()
+    {
+        return Convert::raw2att($this->Name);
+    }
+
+
     public function buildChildren()
     {
         $children = new FieldList();