Method patch not working with joinBy* fields.

[GiuseppeCM]

I try to patch one fields (type:joinBy*), but the only way to do this is:
{"_fieldsName":"","fieldsNameId":"cjraqbk600005cw0wjpj2kot7"}, but it is wrong because the correct way to patch a field is {"fieldsNameId":"cjraqbk600005cw0wjpj2kot7"}.
In documentation : "Include only the properties you wish to change."

I think it's caused because the check into schema about piece is only on "name" attribute and not "idField" or "idsField" for the join fields, so the fields to change is not found and updated.