Add ExtendedRequestId to APIGatewayProxyRequestContext

[DanielBauman88]

It exists on APIGatewayWebsocketProxyRequestContext but not ExtendedRequestId.
It is however present on non-websocket requests and should be accessible by consumers of this package.

• REST https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
• HTTP https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-logging-variables.html

Issue #, if available:

Description of changes:

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[DanielBauman88]

I validated this with my rest api by deploying my go code and replacing this module with my changes. The extended request id is accessible as expected.

This was supported for websocket requests when this was added but this was never supported for non-websocket requests.

This functionality is important so that customers can long the extendedRequestId in lambda code - this will match what's logged in the APIGW execution logs.

[DanielBauman88]

Thanks for enabling the WFs. I noticed they failed on the first revision, pushed a new one and validated that the tests pass locally with

✗ go test -race -coverprofile=coverage.txt -covermode=atomic ./...

ok  	github.com/aws/aws-lambda-go/cfn	0.168s	coverage: 72.2% of statements
ok  	github.com/aws/aws-lambda-go/cmd/build-lambda-zip	17.898s	coverage: 54.7% of statements
ok  	github.com/aws/aws-lambda-go/events	0.450s	coverage: 83.2% of statements
?   	github.com/aws/aws-lambda-go/events/test	[no test files]
ok  	github.com/aws/aws-lambda-go/lambda	1.090s	coverage: 90.0% of statements
?   	github.com/aws/aws-lambda-go/lambda/handlertrace	[no test files]
?   	github.com/aws/aws-lambda-go/lambda/messages	[no test files]
?   	github.com/aws/aws-lambda-go/lambdacontext	[no test files]

[bmoffatt]

https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-input-format validated against docs sample

[bmoffatt]

Thanks!

[DanielBauman88]

Thanks!