docs(event_handler): add section about Pydantic serialization

[leandrodamascena]

Issue number: #6728

Summary

This PR addresses issue #6728 by adding comprehensive documentation about Pydantic serialization behavior when using Event Handler with validation enabled.

Changes

Documentation Updates

• Added new section "Pydantic serialization behavior" in the Event Handler documentation
• Explains that Pydantic models are serialized using by_alias=True by default when enable_validation=True
• Clarifies the difference from Pydantic's default behavior (by_alias=False)

Checklist

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• Meet tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.27%. Comparing base (5999346) to head (8a321a8).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7049   +/-   ##
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  Coverage    96.27%   96.27%           
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  Files          275      275           
  Lines        12912    12912           
  Branches       954      954           
========================================
  Hits         12431    12431           
  Misses         376      376           
  Partials       105      105           

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

[dehanjl]

Awesome, thanks!