Note this feature is optional and the auth is blinded in the same way as e-cash itself. It is a ZK proof, the mint doesn't know the authenticated user.
Discussion
Being optional is irrelevant as such mints would still be considered cashu mints.
Mint knows each authenticated user with a `linkingkey`and account model: https://github.com/cashubtc/nuts/blob/9cb6272e9d1eb26fdfb117318bba825c068e888d/16.md
