Mark new module APIs as experimental

[anoadragon453]

It is not clear that these won't change as people start to play with them. Let's wait to stabilise them in a future release.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
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• Code style is correct (run the linters)

[anoadragon453]

I'm going to assume we can skip the integration tests for this change, and merge.