Sharding news:
Patches are starting to get merged on the admin API side of things. We now have a clear distinction between control plane and data plane storage drivers. This distinction made abstractions easier to cope with further along.
There's also a more encompassing notion of an admin API instance. An admin instance contains all the routes/resources/powers that a public API instance has, plus access to control plane features. In the case of sharding, an admin instance allows an operator to register shards and investigate the state of the catalogue that maps queues to shards.
Next up: finish getting the admin API for sharding merged in, get the catalogue portion reviewed, and then put it all together!