R1:4505724cc4f1

Allow repositories to be bound to an AlmanacService

Summary:
Ref T2783. This is primarily exploratory and just figuring out what we're blocked on:

- Allow a Repository to be bound to a Service. The Service may eventually define multiple read/write nodes, etc.
- There's no UI to do this binding yet, you have to touch the database manually.
- If a repository is bound to a Service, effect Conduit calls via calls to the remote service instead of executing them in-process.
- These don't actually…