feat: Improves guideline extraction pipeline

[frgfm]

This PR introduces the following modifications:

• adds additional sources to the guideline extraction route
• switches back to GPT3.5 Turbo
• adds parallelism utils
• adds Github client methods
• Improves OpenAI calls

[codecov]

Codecov Report

Attention: 46 lines in your changes are missing coverage. Please review.

Comparison is base (75608c2) 83.67% compared to head (37bda9f) 80.90%.

Files	Patch %	Lines
src/app/services/github.py	54.76%	19 Missing ⚠️
src/app/api/api_v1/endpoints/repos.py	10.00%	18 Missing ⚠️
src/app/services/openai.py	33.33%	8 Missing ⚠️
src/app/services/utils.py	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   83.67%   80.90%   -2.77%     
==========================================
  Files          28       29       +1     
  Lines         888      969      +81     
==========================================
+ Hits          743      784      +41     
- Misses        145      185      +40     

Flag	Coverage Δ
unittests	80.90% <50.53%> (-2.77%)	⬇️

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