[michaelteter]

I don't know the details, but I think what you're describing is what the Dutch DigID ( https://www.digid.nl/ ) system provides. It is used on local and national government data portals as well as for legal document signing, etc. It works very well in my experience, and in fact I don't even have to have a username/password on the websites.

[messe]

There's a similar system in Denmark called MitID (my ID), it can even be used by businesses. I can pop into my local REMA 1000, scan my groceries —including alcohol—on my phone, and pay for them all in-app without any interaction with another human being. Because I'm logged in with MitID, there's no need for the additional age verification that more traditional self-scan checkouts require for purchasing alcohol.