Add revision command

[lafrech]

This command is meant to be used by developers to generate migration files.

[codecov]

Codecov Report

Attention: Patch coverage is 53.84615% with 6 lines in your changes missing coverage. Please review.

Project coverage is 95.51%. Comparing base (b9d9c0e) to head (ddad635).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bemserver_core/migrations/__init__.py	37.50%	5 Missing ⚠️
src/bemserver_core/commands.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #258      +/-   ##
==========================================
- Coverage   95.60%   95.51%   -0.10%     
==========================================
  Files          44       44              
  Lines        2776     2784       +8     
  Branches      281      281              
==========================================
+ Hits         2654     2659       +5     
- Misses         97      100       +3     
  Partials       25       25              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.