fix: Google OAuth broken in unified docker image

[jiulongw]

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• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.
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Changes

Allows changing SECURE_CROSS_ORIGIN_OPENER_POLICY Django settings via environment variable.

This setting is set to "same-origin" by default by Django, which effectively blocks Google's OAuth popup window sending access token to Flagsmith.

How did you test this code?

1. Deploy with the Flagsmith unified Docker image to production with https domain.
2. Turn on Google OAuth.
3. Google OAuth flow only works after setting the DJANGO_SECURE_CROSS_ORIGIN_OPENER_POLICY to same-origin-allow-popups in the environment variable.

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Name	Status	Preview	Comments	Updated (UTC)
docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 19, 2024 4:09am

[matthewelwell]

Thanks for this @jiulongw!

[github-actions]

Uffizzi Preview deployment-58325 was deleted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.35%. Comparing base (9bbfdf0) to head (16ff185).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4839   +/-   ##
=======================================
  Coverage   97.35%   97.35%           
=======================================
  Files        1182     1182           
  Lines       41272    41273    +1     
=======================================
+ Hits        40179    40180    +1     
  Misses       1093     1093           

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[matthewelwell]

@jiulongw can you fix the linting errors here and we can get this merged.

[jiulongw]

@matthewelwell thanks for reviewing! Just fixed the formatting.