Hey Phuturist!
I had the same needs and I found a way to have the informations in JSON about who initiated change.
In the API, when you’re initiating a change in lockstate, you receive in JSON a thing like Nuki Web().
You can pass a descriptions beetwen those parenthesis by sending a POST request to https://api.nuki.io/api/key/:id and updating the description params with a string.
You can see it here : Swagger UI
I’m making this everytime someone lock/unlock the door. I pass the user ID and other important information and then parse the string to retrieve the ID and identify the user who did the change with this.
It need a bit of development but this a great way to have what you’re describing here!
Hope this help you and some others! 