If a membership is set to "Unused classes roll into the next period", the classes
a member did not use should be added to their next period. Three problems could
stop that from happening, and they are fixed.

**Leftover was lost when the membership renewed.** Whether the classes carried
over depended on whether the renewal payment or the nightly update reached the
membership first, which in turn depended on the time of day the member first
signed up. When the renewal came first, the leftover was reset to zero. It now
carries over in both orders.

**Memberships sold with an aligned first period never carried anything over.**
A Flexible membership sold so that its billing day lines up with the venue's
billing day has a first period that starts before that billing day. Leftover
from that first period was ignored. It now carries into the second period.

**The leftover cap and the pause option were not applied.** The settings
"Cap at this period's grant", "Cap at a number of classes" and "Carry leftover
while the membership is paused" were saved but no longer took effect for
recurring memberships, so leftover always stacked without limit and a paused
member never kept it. They apply again exactly as they are described in the
editor. A membership that has not started yet, or that is cancelled, terminated,
expired or suspended, still carries nothing over.

Members who have carried classes can now also book them: a member who had used
the number of classes they bought was previously refused a class that their
carried classes covered.

Nothing changes for memberships where the unused-classes option is off, which is
the default, and no member's balance is edited by hand. Balances follow the new
rules the next time they are recalculated, which happens every night and whenever
a member books or cancels.