Add support for Apigatewayv2 payload 2.0

[NicolasSeiler]

Add support for the new payload version of the apigatewayv2.
https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html

[dherault]

I've come to understand that this is not a breaking change, is that correct?
Thanks a lot, will merge asap

[natac13]

Hey, thank you so much for this PR. I was really having some trouble with the API v1 vs v2 payloads.
Before this was merged I forked the master branch and applied these changes locally so that I can tests things out using the instruction in the contributing.md file.
However, the Graphql Playground does not seems to work even those the serverless lambda is up and running and my client application can connect fine.

The playground shows up but no Docs, Schema and say it received a 404 response.

Hopefully this was just something I did wrong and wont be an issue one this is merged. I just wanted to mention something just in case.

Again thank you for this PR and hopefully it can be merged soon 🤞

[dherault]

Thanks @NicolasSeiler, v6.8.0