immutable snapshot of the current state of the world. It is regenerated (usually partially) on each configuration push (more on this below). Due to being a snapshot, most lookups are lock-free.

`PushContext` is built up by querying the above layers. For some simple use cases, this is as simple as storing something like `configstore.List(SomeType)`; in this case, the only difference from directly exposing the configstore is to snapshot the current state. In other cases, some pre-computations...