feat(event_handler): use custom serializer during openapi serialization

[rubenfonseca]

Issue number: #3892

Summary

Changes

Please provide a summary of what's being changed

This PR modifies the OpenAPI validation middleware to use the any custom serialized provided by the user on the event handler, when the normal serialization mechanisms fail.

This allows you to use your own custom serializer when returning custom objects
from the handlers.

User experience

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

def test_openapi_serialize_other(gw_event):
    # GIVEN a custom serializer
    def serializer(_):
        return "hello world"

    # GIVEN APIGatewayRestResolver is initialized with enable_validation=True and the custom serializer
    app = APIGatewayRestResolver(enable_validation=True, serializer=serializer)

    # GIVEN a custom class
    class CustomClass(object):
        __slots__ = []

    # GIVEN a handler that returns an instance of that class
    @app.get("/my/path")
    def handler():
        return CustomClass()

    # WHEN we invoke the handler
    response = app(gw_event, {})

    # THEN we the custom serializer should be used
    assert response["body"] == "hello world"

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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[leandrodamascena]

Hello @rubenfonseca! I just left some small suggestions to improve code maintenance and I would like to hear your opinion on the question I asked.

Thanks, Ruben! This is a great improvement.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[leandrodamascena]

APPROVED!!