I'm working on setting up a sharded cluster. Do all replica sets in a cluster need to have unique names? Normally I would name each replica set something like "rs1", "rs2", etc. but the automation I'm using right now is currently setting each replica set name to just "mongo". Can multiple replica sets with the same name – each acting as a shard – be part of the same cluster? Or do the replica set names need to be unique across the cluster?