[New Feature] JournalStore should be able to partition by date

[cstamas]

Or even something more generic solution, like some Function<Something, PartitionId> and on new partition ID KZ would close current, create new one and append....

Then, "specialisations" could be things like:

• ByCalendarDayFunction
• ByCalendarYearFunction
• BySomeAppSpecificRecordContentFunction
• ...

Just throwing in idea.

FTR: this comes from NX Timeline, where journal could be partitioned "by calendar day", purge operation would become nearly trivial, as it would become just dropping closed partitions that are older than N days.

[sunnygleason]

This is an awesome feature request. Other things may take priority, but I will schedule this as soon as I can after those because it's especially cool.