Returned by GET /api/community?period= to the Community page, and
gathered by community-service.ts, which the digests read too.
from: Date
The period covered, from from to to.
to: Date
In sign-up order, each with invitedByUsername when someone invited them.
chatMessages: number
totals: { dumps: number; upvotes: number; comments: number; }
Public dumps posted, upvotes cast and comments written in it.