Scaffold nuxeo-directory-radio-group bound to selectedItem instead of value

When d&d a directory field from the Designer toolbox using the Radio group option, we currently scaffold the element nuxeo-directory-radio-group with the field bound to the value attribute. Using this in a layout, the widget is never updated with the correct directory entry, unless we bound the field to the selectedItem property.

How to reproduce:

• Define a new document type in Studio Modeler with a directory property (e.g. on directory language)
• in Studio Designer use element nuxeo-directory-radio-group for the custom property in layout create/edit and metadata (d&d from option `Radio group`)
• deploy
• log in the Web UI
• Create a document with the new document type created in Studio Modeler and select a directory entry (portuguese, for instance)
• Confirm that the directory is not selected in the metadata layout, or in the edit one

Expected result: custom field shows the correct language selected
Actual result: no selection is displayed