Up to v5.0 (included), the shards pass the collection namespace to the _configsvrMoveChunk command but not the collection UUID, so the parser expects the namespace as mandatory argument.

In v5.1+, the shards pass both the collection namespace and UUID, so the parser expects the namespace as mandatory argument and the UUID as optional (prior to this change, the UUID was expected instead).

From v6.0, the collection UUID will be a mandatory argument of the command. The implementation of shard (caller) and config server (receiver) must be adapted as a consequence (see TODOs).