Set up A/B testing

[sterlinghirsh]

It came up in #1463 that we wanted to A/B test the new add-to-cart bar, but we haven't tried A/B testing on react-commerce yet. We have done this on other parts of the site in the past, but it will work differently in nextjs. Will it work through GA? Matomo? How will caching work? As a proof of concept, we can set up a dummy A/B test with no difference and confirm that both groups perform about the same. Then I'd like to try testing with/without the add-to-cart bar.

[danielbeardsley]

I would love to work on this and figure out how to implement it cleanly in this situation.

[danielbeardsley]

Google Optimize sunset's on Sept 30th. It will continue to work before then, we have a lot of experience with it, and creating and using a new server-side experiment is not hard:
https://developers.google.com/optimize/devguides/experiments?technology=ga4