The test cases need to distinguish the scenarios
- for an auth'ed user that has no advance_cluster_time privilege (mongos signs clusterTime)
- for an auth'ed user that has advance_cluster_time privilege (mongos does not sign clusterTime)
- case when auth is disabled. (mongos does not sign clusterTime)
jstests/multiVersion/causal_consistency_upgrade_cluster
jstests/multiVersion/causal_consistency_downgrade_cluster
jstest/sharding/mongos_does_not_gossip_logical_time_without_keys