Rollups so the control plane need not derive them from every row.
bySchemaVersion says whether the fields about to be read can be trusted: a consumer that
assumes one shape mid-rollout reads the other version's defaults as data.
sites whose last report is older than the heartbeat, so their state is not current
sites the inventory believes are unwell, named rather than counted
the rollups a control plane opens with, plus the names of stale and unhealthy sites