Setup wagtail-ab-testing tracking script

[jhonatan-lopes]

Description

Setup the tracking script for wagtail-ab-testing to be compatible with our CSP.

Link to sample test page:

• A/B test page: https://foundation-s-feature-fi-ks2aui.mofostaging.net/en/blog/initial-test-blog-post-with-fixed-title/
• Goal page: https://foundation-s-feature-fi-ks2aui.mofostaging.net/en/
• A/B test stats: https://foundation-s-feature-fi-ks2aui.herokuapp.com/cms/pages/13/edit/

Related PRs/issues: #11890

Testing

1. Go to "A/B test stats" page and note the number of participants in each group (control vs variant)
2. Go to the "A/B test page" and note if it is a control or variant (the variant's title starts with "[A/B test]")
3. At the "A/B test stats" page, check that the sample size increased by 1 but the number of conversions in your test (control or variant) was kept constant
4. Go to the "Goal page" to register a conversion
5. Go back to the "A/B test stats" page and check that now the number of conversions in your test group (control or variant) has increased by one

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

[robdivincenzo]

Looks good @jhonatan-lopes !

[robdivincenzo]

@jhonatan-lopes Not related to this pull request, but as a follow-up, there are concerns with the dashboard's visibility on the dark theme. Are we tracking that issue somewhere?

[jhonatan-lopes]

Hey @robdivincenzo, thanks for flagging that up! It's being tracked on wagtail-nest/wagtail-ab-testing#62, and I'm working on it!