fix typo
Initial work at replacing the dynamic registration_item with a built-at-creation one. (incomplete, requires update logic)
add task which will roll over registration periods to the new one (for all registrants with reg items)
add a banner if the update function hasn't been run in 3 days
update documentation to include scheduler task required for reg-period-updater
prevent creating a registrant when there isn't an active registration_period
undo the requirement that registration_period exists when creating registrant. Also allow registrants to be deleted if they do not have any paid-payments