Field validation not triggered for a schema dynamically added

Steps to reproduce:

• Have a schema with a required field
• Add it to a facet definition
• In emptyDocCreated, add the facet (Document.AddFacet, without saving because we are in emptyDocCreated)
• Save document without filling the required field
• => no error triggered.

Notice : in this use case, the field is not displayed in the UI (so WebUI does not do anything special)

The document is created, its JSON show the facet is there and the field is there, null.

Expected: Creation should have been rejected.