Move in-page script to tracker.js

[jhonatan-lopes]

Move the window.wagtailAbTesting in-page script to tracker.js. This will allow for a better CSP control as we move away from in-line scripts.

In addition, the logic to get the parameters necessary for tracking has been offloaded from the script to the template tag function.

Finally, the data is now passed to tracker.js via the json_script built-in Django template filter, which takes care of JS escaping and is compatible with a strict CSP.

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 88.40%. Comparing base (54f244c) to head (162e707).

Files	Patch %	Lines
...ab_testing/templatetags/wagtail_ab_testing_tags.py	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #73      +/-   ##
==========================================
+ Coverage   87.84%   88.40%   +0.55%     
==========================================
  Files          15       15              
  Lines         732      750      +18     
  Branches      137      140       +3     
==========================================
+ Hits          643      663      +20     
+ Misses         54       51       -3     
- Partials       35       36       +1     

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[Stormheg]

Amazing – thank you so much @jhonatan-lopes! ❤️

Quick question: is this the only change we need to make to be CSP compatible? If it is, I'd say we can advertise CSP compatibility in the readme!

[jhonatan-lopes]

I think this should be enough to make it CSP compatible. Yep, advertising it in the README sounds like a great idea