CIP: add notify mechanism for indicating a revoked reservation

In the current CIP API, the client invokes a license reservation, but after the initial request there's no possibility to check any status changes of the active reservation.

In case the reservation expires, for example due to failed renew requests, the client should be informed that the reservation is not valid anymore.

Another question is, do we need to allow notifying other reservation status changes, like that a renewal was made? For example the lease time gets updated during renewal, and if the client wants to present that information to end-user, it becomes outdated after the first renewal without notifying the client.