refactor(event_handler): extract OpenAPI schema generation from Route class

[leandrodamascena]

Issue number: closes #8097

Summary

• Extract OpenAPI schema generation from Route into openapi/schema_generator.py with standalone functions
• Move _DEFAULT_CONTENT_TYPE and _DEFAULT_OPENAPI_RESPONSE_DESCRIPTION to openapi/constants.py
• Route._get_openapi_path now delegates to generate_openapi_path()
• No public API changes — all moved methods were internal (_ prefixed)

Changes

Please provide a summary of what's being changed

User experience

Please share what the user experience looks like before and after this change

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
2.3% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 97.28261% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.62%. Comparing base (7323c05) to head (b853c9f).

Files with missing lines	Patch %	Lines
...wertools/event_handler/openapi/schema_generator.py	97.17%	1 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8098      +/-   ##
===========================================
- Coverage    96.63%   96.62%   -0.01%     
===========================================
  Files          283      284       +1     
  Lines        13862    13881      +19     
  Branches      1111     1110       -1     
===========================================
+ Hits         13395    13413      +18     
- Misses         342      343       +1     
  Partials       125      125              

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