Format and improve Alembic migration generation

[armanddidierjean]

Description

• import app.type.sqlalchemy.TZDateTime in migration files for custom DATETIME objects
• lint and format migration files
• don't put the migration revision and down_revision in the file docstring as we usually forget to update them

Checklist

• All tests passing
• Extended the documentation, if necessary

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.47%. Comparing base (b3454a0) to head (477583d).

❗ Current head 477583d differs from pull request most recent head 310a562. Consider uploading reports for the commit 310a562 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #396   +/-   ##
=======================================
  Coverage   80.47%   80.47%           
=======================================
  Files          86       86           
  Lines        5766     5766           
=======================================
  Hits         4640     4640           
  Misses       1126     1126           

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[julien4215]

Maybe we could add a comment in the datetime.py file to explain that if we change the custom type then it might break the existing migrations.