Relevant docs on primary actions: Actions — ash v3.29.3
I considered making the generators add a primary read action, but users is a pretty sensitive resource and I wanted to add only the minimal required to power authentication.
You will also need to add authorize?: false to your call because of the policies on users. A mild inconvenience, but the security benefits are worth it 
So after adding a primary action: Ash.get!(User, <id>, authorize?: false)
