feat(event_handler): enable support for custom deserializer to parse the request body

[LucasCMFBraga]

Issue number: #6600

Summary

This feature allows to pass a custom deserializer to ensure accurate handling of floating-point precision.

Changes

Added support for passing a custom deserializer instance to ApiGatewayResolver to handle JSON numeric values as Decimal, ensuring correct floating-point precision.

`
from tests.functional.utils import load_even
import json
from decimal import Decimal

app = ApiGatewayResolver(deserializer=partial(json.loads, parse_float=Decimal))
`

User experience

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

`
app = ApiGatewayResolver(deserializer=partial(json.loads, parse_float=Decimal))

@app.post("/my/path")
def test_handler():
    return app.current_event.json_body

# WHEN calling the event handler
event = {}
event.update(LOAD_GW_EVENT)
event["body"] = '{"amount": 2.2999999999999998}'
event["httpMethod"] = "POST"

result = app(event, {})
# THEN process event correctly
assert result["statusCode"] == 200
assert result["multiValueHeaders"]["Content-Type"] == [content_types.APPLICATION_JSON]
assert result["body"] == '{"amount":"2.2999999999999998"}'

`

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• 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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[boring-cyborg]

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[leandrodamascena]

Hi @LucasCMFBraga, thanks for working on this PR! I've reviewed it and to me it makes sense for us to add these new parameter to propagate it to DataClasses, but I'm wondering if we're parsing float incorrectly and if it would make sense to make it default here: https://github.com/aws-powertools/powertools-lambda-python/blob/develop/aws_lambda_powertools/utilities/data_classes/common.py#L89

WDYT?

[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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.12%. Comparing base (d00c6a1) to head (9448f97).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6601   +/-   ##
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  Coverage    96.12%   96.12%           
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  Files          253      253           
  Lines        12104    12105    +1     
  Branches       902      902           
========================================
+ Hits         11635    11636    +1     
  Misses         369      369           
  Partials       100      100           

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