Sharding mostly does not interact with replicated record ids, as a sharded collection can have different idents on different shards without causing any problems. The possible exception is resharding, which generates new index idents as part of creating the temporary resharding collection. This appears to be a valid place to generate idents, but we should double-check that everything is sensible and write a test which verifies that the catalog is consistent within each shard after running resharding.