The JSON for the base user record can be found in Github here: https://github.com/folio-org/mod-users/blob/master/ramls/userdata.json
One thing that's important to understand is that, with the appropriate permissions, you will see much more on a user record in the Users app UI than is actually part of the underlying base record. For example, in the FOLIO UI, you could see all of these accordions on a user record: