refs https://github.com/TryGhost/Team/issues/1306
- Contains all services that listen on member events
- Only contains the last-seen-at-updater service for now
- Listens for `MemberViewEvent` events to update the `member.last_seen_at` timestamp
- Updates after 24hours of the last timestamp to avoid too many writes
- Also updates when the value is NULL
- This is using the existing `last_seen_at` value to avoid an SQL query when no writes are required
