I would like to restrict the set of bookies to be used for a specific ledger. Actually a single EnsemblePlacementPolicy is used for all the ledgers.
This is because I want to create a ledger only using a dedicated set of machines/bookies which are dedicated to the 'tenant' for which I'm creating the ledger.
We can add an optional (byte) parameter to asyncCreateLedger which in turn is to be passed to the configured EnsemblePlacementPolicy which in turn will be able to decide which are the most suitable bookies for the tenant.
This parameter must be stored on ledger metadata, in order to be used in replaceBookie.