If you're not sure how you want to do this, you could always wait until you need to implement version 2. You would then be forced to have omission of a version

If you're not sure how you want to do this, you could always wait until you need to implement version 2. You would then be forced to have omission of a version number indicate version 1, but waiting would allow you to make the decision when you're actually ready to begin implementation and might have a better idea or more information about how you want to approach it.