fix(event_handler): match generic alias response models in OpenAPI schema

[TanbirRamim]

Issue number: closes #8450

Summary

Changes

Since custom responses started being deep-copied before their model is resolved, a generic alias such as list[Model] comes back as a new GenericAlias object, so the identity check in _resolve_response_payload never found the matching field and get_openapi_schema() raised StopIteration. This compares the model with == instead of is; plain classes still compare by identity, and generic aliases compare structurally. I added a regression test in test_openapi_responses.py covering list[Model] and dict[str, Model], which fails with StopIteration before the change and passes after; the event_handler functional tests, ruff and mypy all pass locally.

User experience

Before, any route with a generic alias as a custom response model broke OpenAPI schema generation, Swagger and validation setup with StopIteration. After, those routes produce the expected array or object schema again, as they did up to 3.24.0.

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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

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[leandrodamascena]

Thanks Tanbir, this is a very good fix. I reproduced the StopIteration on develop and confirmed that both list[Model] and dict[str, Model] generate the expected schemas with this change.

Using equality here makes sense because deepcopy creates a new generic alias, while regular model classes keep the same behavior. I’ll approve and merge this.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.65%. Comparing base (237f4db) to head (0df6ff7).

Additional details and impacted files

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##           develop    #8453   +/-   ##
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  Coverage    96.65%   96.65%           
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  Files          296      296           
  Lines        14905    14905           
  Branches      1266     1266           
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  Hits         14407    14407           
  Misses         363      363           
  Partials       135      135           

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[boring-cyborg]

Awesome work, congrats on your first merged pull request and thank you for helping improve everyone's experience!

[powertools-for-aws-oss-automation]

Awesome work, congrats on your first merged pull request and thank you for helping improve everyone's experience!