editoast: update modified field of infra upon modification

[leovalais]

Part of editoast-statful scalability work.

The field used to default to NOW() on INSERT, but was never updated.

Naive datetimes are also replaced by DateTime<Utc>.

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Codecov Report

Attention: Patch coverage is 98.48485% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.92%. Comparing base (66a9cad) to head (23c96c1).
Report is 22 commits behind head on dev.

Files with missing lines	Patch %	Lines
editoast/src/infra_cache/operation/mod.rs	88.88%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #10716      +/-   ##
==========================================
- Coverage   81.93%   81.92%   -0.01%     
==========================================
  Files        1079     1079              
  Lines      107376   107533     +157     
  Branches      737      734       -3     
==========================================
+ Hits        87978    88096     +118     
- Misses      19358    19397      +39     
  Partials       40       40              

Flag	Coverage Δ
editoast	74.37% <98.48%> (+0.09%)	⬆️
front	89.41% <ø> (-0.07%)	⬇️
gateway	2.18% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.50% <ø> (ø)
tests	88.14% <ø> (ø)

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[hamz2a]

Thanks for the PR! I left a small suggestion for a non-blocking change.

[woshilapin]

How about moving that logic to the DB so we don't forget to put it in every places in the code that needs it? I usually don't like putting logic in the DB, but in this case, it looks almost like a missing feature of Postgres (MySQL seems to have syntactic sugar for it).