Tighten lambda-http event deserializer

[bnusunny]

Issue #, if available:

related to awslabs/aws-lambda-web-adapter#317

Description of changes:

Add 'deny_unknown_fields' to ApiGatewayProxyRequest, ApiGatewayV2httpRequest, and ApiGatewayWebsocketProxyRequest. This prevents the runtime to deserialize Bedrock Agent event as 'ApiGatewayProxyRequest'.

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• I confirm that I've made a best effort attempt to update all relevant documentation.

[calavera]

We just removed those attributes in #753. Can we do anything else to improve the serialization logic besides that?

[bnusunny]

The schema for these HTTP related events rarely change. For breaking changes, the service team usually publishes another version of the schema. For example, APIGW v1 and v2.

[calavera]

Why are bedrock events being mistaken with APIGW events? they are two completely different services. I'd prefer to fix that.

[bnusunny]

Yes, they are two completely different services and schema. But 'ApiGatewayProxyRequest''s properties are either optional or have defaults. 'ApiGatewayWebsocketProxyRequest' has the same problem.

'ApiGatewayV2httpRequest' has 'skip_serializing_if' on several properties. 'AlbTargetGroupRequest' has one mandatory property 'http_method'.

One solution is to use 'skip_serializing_if' on 'ApiGatewayProxyRequest' and 'ApiGatewayWebsocketProxyRequest'.

[bnusunny]

I'm puzzled: the SQS event has no issue. Only Bedrock one has this issue.

[bnusunny]

I found the reason. Bedrock event has 'httpMethod'. This single property made it deserializable into 'ApiGatewayProxyRequest' and 'ApiGatewayWebsocketProxyRequest'.

[bnusunny]

@calavera I have updated the PR. Please take a look again.

[calavera]

LGTM!