There are only three valid combinations for versioning a command with the shard version and database version (<DBV, SV>):

• <dbVersion, UNSHARDED> → Targets an unsharded collection located in the database's primary shard.
• <dbVersion, boost::none> → Targets the database's primary shard.
• <boost::none, shardVersion> → Targets a sharded/tracked collection.

Any other combinations are incorrect and may introduce bugs in the future.

The goal of this ticket is to ensure that no code sends a command versioned with an invalid combination of DBV and SV.