feat: Issue 166 json formatted logs

[masmontanas]

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Changes

Extending logging.Formatter with a custom class for json formatted messages. Unfortunately specifying json format as a string in the LOGGING dictionary presented a corner-case with the axes module (which returns a dictionary [with double-quoted values] with request information). Traditional string formatting tokens also had to be replaced with '{}' since the tokens were not being interpolated properly after the logging formatter was added.

How did you test this code?

1. Build flagsmith:local container locally.
2. Update docker-compose.yaml to use flagsmith:local container.
3. Update environment variables in docker-compose file to include LOG_FORMAT: json
4. Basic local testing through the UI to ensure logs were properly formatted.

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Name	Status	Preview	Comments	Updated (UTC)
docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Feb 13, 2024 5:32pm

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[matthewelwell]

Hi @masmontanas, thanks for this PR, it looks really good on the whole! I've added a few minor comments but I think we can get this merged very soon for sure.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 95.91%. Comparing base (da21b8c) to head (d7a0746).
Report is 921 commits behind head on main.

Files with missing lines	Patch %	Lines
api/util/logging.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3376      +/-   ##
==========================================
- Coverage   95.93%   95.91%   -0.03%     
==========================================
  Files        1077     1083       +6     
  Lines       32950    33612     +662     
==========================================
+ Hits        31612    32240     +628     
- Misses       1338     1372      +34     

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[masmontanas]

Hi @matthewelwell , required updates are ready for review. Thank you.

[masmontanas]

Hi @matthewelwell , I saw that e2e tests failed but doesn't seem to be related -- anything needed from my end?

[khvn26]

I'm approving this, but we need to be conscious that, from observability perspective, it isn't a great solution.

We need to evaluate integrating something like https://django-structlog.readthedocs.io/en/latest/ so Flagsmith provides truly insightful structured logs in the future.

[matthewelwell]

@masmontanas I've approved, but it looks like you have some legit test failures to resolve.

[masmontanas]

Fixed unit test issue.

[matthewelwell]

thanks again @masmontanas !