Support explicitly specifying "no version" on a request #35566
Description
When a request is prepared, as a client or in tests, you can choose to either specify a version or not specify it. If you don't specify it, the request won't have a version, unless a default version is configured.
It would be useful to provide a way to explicitly indicate that the request should not have a version. The most straight forward way to do that is by accepting null where the version can be provided.