Repose | End date for periodic schedule

The ePROMs (periodic symptom check (= "normal" symptom check active 2 days a week)) should end automatically after 6 months (180 days).

Either extend the periodic schedule functionality to accept an end date OR a number of days that the SC is active for. Note that not everyone starts the study on the same day, so this has to be dependent on the day of the first app use. See also !690, ReposeSporadicSymptomCheckStore does the same thing for sporadic SCs.

or create the ePROMs as a sporadic SC, but make sure that it's active only on Wednesday and Saturdays (maybe switch statement checking which day of the week startDate is and filling in interval accordingly?)