Maintain a content group with MetaBroadcast picks, based on
prime-time broadcasts from a provided channel group.
If the lower bound to the Range provided to DayRangeChannelDaySupplier was open, then
the generation of ChannelDays failed, since the termination condition checked that
the current day, starting at the lower bound, is in the range. That does not hold
for the initial value when the lower bound is open.