Reports are immutable history, so a node that migrated has reports in the
old PuppetDB and the new one; serve the union rather than picking a single
owning backend as /facts does.
Re-apply order_by/limit/offset over the merged set and sum X-Records, since
each backend only orders and pages its own slice.
Split out from node-lookup PR #17 into its own repo. pdbmux presents a
single merged PuppetDB v4 query surface over the old (Consul) and new
(k8s) PuppetDBs during the VM to k8s migration, and is deployed in-cluster
via argocd-apps as a container image.