split API between scopes (set of bitmasks) and named_scopes (scope + uuid) ?

[perarnau]

There are several points in the API or in client code where we would like to operate purely in the set of resources that a scope represent,
without caring for its name.

It would be useful to split the type in two, maybe make the named one public, and simplify the tooling around scopes a bit.

[perarnau]

The other option is to mostly use scope uuids internally, and keep the full scope type to only exist at the interface between daemon and clients. The advantage is that scope uuids can be refcounted nicely, which isn't the case for other objects at this point.