Non-addressable collections?

[ThisIsMissEm]

Currently all collections of actors are addressable by default, which means you can't expose a collection of actors without that being able to be used for addressing.

If a recipient is a Collection or OrderedCollection, then the server MUST dereference the collection (with the user's credentials) and discover inboxes for each item in the collection. Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.

However, I think there are cases where we want a collection to not be able to be used for addressing, but it'd be tricky / best-effort now to say something like addressable: false on the collection.