Function book_triggered_fetch 

pub async fn book_triggered_fetch(
    conn: &mut PgConnection,
    course_code: &str,
    books_follow_up: bool,
) -> ModelResult<bool>

Books a listing for an unlinked student’s visit or check request, with account linking on: at the earliest an hour after the last listing, and for a visit also one follow-up two hours on. Refused once the code has had its triggered listings for the day. Returns whether anything was booked.