refactor: robustness and localdev

[alexgarel]

What

• make some part of the code and settings more compliant to a use with a local deploy of product opener
• settings had a dangerous pattern in the object to get domains, fixed it.
• also made scheduler more resilient to not having network

Note: a more serious refactor of networks between docker should be done, but later...

This was done to be able to test openfoodfacts/openfoodfacts-server#7379

[codecov]

Codecov Report

Merging #906 (aba99d5) into master (cdab35f) will increase coverage by 0.03%.
The diff coverage is 92.00%.

❗ Current head aba99d5 differs from pull request most recent head eff625d. Consider uploading reports for the commit eff625d to get more accurate results

@@            Coverage Diff             @@
##           master     #906      +/-   ##
==========================================
+ Coverage   52.80%   52.83%   +0.03%     
==========================================
  Files          92       92              
  Lines        7034     7045      +11     
==========================================
+ Hits         3714     3722       +8     
- Misses       3320     3323       +3     

Impacted Files	Coverage Δ
robotoff/off.py	31.95% <0.00%> (-0.14%)	⬇️
robotoff/prediction/ocr/image_flag.py	41.02% <ø> (ø)
robotoff/scheduler/__init__.py	47.79% <66.66%> (+0.06%)	⬆️
robotoff/slack.py	91.33% <89.74%> (ø)
robotoff/app/api.py	49.30% <100.00%> (ø)
robotoff/app/core.py	91.86% <100.00%> (ø)
robotoff/settings.py	96.66% <100.00%> (+0.13%)	⬆️
... and 2 more

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
6 Security Hotspots
122 Code Smells

0.0% Coverage
0.1% Duplication

[raphael0202]

See attached comments

[alexgarel]

I've done requested changes @raphael0202