Add wagtail-ab-testing

[jhonatan-lopes]

Description

Add wagtail-ab-testing package to enable A/B testing of pages.

A sample A/B test can be found under the English homepage of the review app: https://foundation-s-feature-wa-ioubyy.herokuapp.com/cms/pages/3/edit/

To create an A/B test:

1. Edit a page
2. Click "Save and create A/B Test"
3. Fill out the required info

Link to sample test page: https://foundation-s-feature-wa-ioubyy.herokuapp.com
Related PRs/issues: #11446

Checklist

Tests

• [ ] Is the code I'm adding covered by tests?

Changes in Models:

• [ ] Did I update or add new fake data?
• [ ] Did I squash my migration?
• Are my changes backward-compatible. If not, did I schedule a deploy with the rest of the team?

Documentation:

• Is my code documented?
• Did I update the READMEs or wagtail documentation?

Merge Method
💡❗Remember to use squash merge when merging non-feature branches into main

[jhonatan-lopes]

wagtail-ab-testing is missing a migration, which is causing the CI to fail. A PR has been submitted to address this upstream.

[jhonatan-lopes]

An outdated stylesheet is causing problems with whitenoise: wagtail-nest/wagtail-ab-testing#66

[mtdenton]

Thanks @jhonatan-lopes !