This introduces `LocalSiteManager`, which is the new manager for `LocalSite` objects. It provides methods used to quickly make determinations about the Local Site usage on the server. The main method currently is `get_stat()`, which returns a dictionary containing: 1. The total number of Local Sites on the server 2. The number of public Local Sites 3. The number of private Local Sites 4. A UUID representing the generated state (which can be used as a component of other cache keys to enable automatic invalidation) This is cached and invalidated any time a `LocalSite` is created, deleted, or if the `public` state has changed, making it fast and reliable for lookups. There are additional wrappers around this that leverage the cached state. These include: * `has_local_sites()` * `has_public_local_sites()` * `has_private_local_sites()` These will soon be used to make some parts of our queries conditional on their presence, letting us simplify queries in the common case.