How to save a different key than the displayed key in an autocompletion widget

Hello,

I'm trying the autocompletion widget. I want to be able to select one bonita user from the registered bonita users and retrieve his id.
I want to display the following key : firstname + " " + lastname, but I want to store in my selectedUser variable another key (the id for instance). My problem is that the key displayed is also the key stored in the variable specified in the value field of the autocompletion widget (selectedUser), and I don't find a way to retrieve the id or the whole user in json format instead.

Is that possible with the autocompletion widget ? It was possible in previous Bonita versions using a map of key / value pairs to display in the autocompletion widget.

Best regards,