Reception.Key's ID should not be string, but a type

[ktoso]

Then we can avoid this:

distributed actor VegetableChopper: Chopping {

  @ActorID.Metadata(\.receptionID)
  var receptionID: String

  init(actorSystem: ActorSystem) async {
    self.actorSystem = actorSystem

    self.receptionID = "*" // default key for "all of this type"
  }
}

and we can do instead:

    self.receptionID = .default // default key for "all of this type"