Adds an index on RealmAuditLog for the realm, event_type, and
event_time in order to improve database queries on these audit logs.
tabbott verified using EXPLAIN ANALYZE that this also considerably
speeds up queries that order by ID rather than event_time, but
event_time is how these should be ordered given the possibility of
backfills.
Adds a support action for updating the minimum licenses on a
customer object once a default discount has also been set.
In the case that the current billing entity has a current active
plan or a scheduled upgrade to a new plan, then the minimum
licenses will not be updated.