Get Internal Freshness Detail

Both freshness grains for one tenant, in a single call.

groups is the FULL rollup, including the groups in apps.freshness.grouping.HIDDEN_FROM_TENANT_GROUPS; the tenant-facing feed filters those out at the endpoint, so this response is a superset of what the tenant panel renders. datasets is every dataset_type behind it, including the ones the taxonomy excludes (flagged excluded, with a null group_key).