Repository state tracking stores
Adds an in-memory and a Postgres implemenation of repository state tracking stores. The two tables added are:
-
repositories
which contains the expected state of repositories in the virtual storage. -
storage_repositories
which contains the state of the repositories on the physical storages.
Cross-referencing these two makes it easier to identify outdated repositories.
This commit implements only the stores without hooking them up to the rest of the code.