Infrastructure

Looking at the ReserveIdentifierService code, the only check on an identifier that it's not already in use is doing a lookup in the Hz system metadata map, which only has PIDs as keys. A possible solution is to use CN.resolve (or CN.getSystemMetadata) instead, but need to check that it's appropriate to introduce a dependency on the CN rest service.

The impact is that hasReservation doesn't give a reliable result.