The SQL schema in the Solena repository doesn't work, because it lacks a default value for some fields in the token table. This makes the registration form fail because it's not setting values for those fields when creating a new registration token.

This adds DEFAULT '' to fields mail, uid, givenName, and sn, making the schema file match what we have in the production server.

Tested in a local VM, registration form gets through and sends the confirmation email (or tries to).