As a host in Portugal, I am required to submit ID details of all guests to the Portuguese government, along with check-in and check-out details. It would be good if the app could handle asking the guests for their IDs, and making the details available to me for sending to the government, so that I do not have to ask for them myself when the guests arrive.
We have to do it in Thailand, then submit the details on a web site, It is only needed if the guest want to extend their stay in Thailand simple enough,
I never ask before they arrive, when they arrive they have to show me their passport I take a photo of that.