User are marked as verified after a join code is redeemed. The user is
redirected to Users::VerificationsController, either:
- after submitting a valid magic link code,
- or immediately after redeeming the join code (if they're already
authenticated with the correct identity)
Account owners are automatically verified when the account is
created (because they have already provided a magic link code at that
point).
This sets up for later commits that will backfill existing users and
require verification before sending notification emails.
Co-Authored-By: Claude <noreply@anthropic.com>