Function seed_frozen_registration 

async fn seed_frozen_registration(
    conn: &mut PgConnection,
    cx: &SeedContext,
    course_id: Uuid,
    course_instance_id: Uuid,
    person: usize,
    last_name: &str,
    state: CreditRegistrationState,
    error_code: Option<CreditRegistrationErrorCode>,
) -> Result<()>

One student, one completion and one ledger row parked in state.

person is the PP half of the student number, in the teacher-views block. The first two get a student number too, one link-verified and one manual, because the teacher view renders them differently.