chiadapter: support API Gateway Events V2

[iamsalnikov]

Issue #134

Description of changes:

I've implemented the support of Gateway Events V2 in chiadapter. I am not sure if everything is ok with the style you prefer, please, feel free to review it and I'll fix all the issues :)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[iamsalnikov]

I've fixed failing tests in #137

[iamsalnikov]

Failing tests are fixed in #131

[iamsalnikov]

I've synced the branch with master to fix the tests.

[iamsalnikov]

Can anyone review and merge it if everything is ok?

cc @sapessi, @drakejin

[zekth]

Can we land this please? @sapessi @drakejin ?

[kateile]

Can we merge this

[miki725]

as lambda urls only work with v2 format, this would be very useful if can be merged

https://docs.aws.amazon.com/lambda/latest/dg/urls-invocation.html#urls-payloads

[drakejin]

Oh my god. I am a maintainer! I didn't notice!

[drakejin]

https://github.com/awslabs/aws-lambda-go-api-proxy/pull/103 https://github.com/awslabs/aws-lambda-go-api-proxy/pull/136 https://github.com/awslabs/aws-lambda-go-api-proxy/pull/156 https://github.com/awslabs/aws-lambda-go-api-proxy/pull/163

@sapessi It's the same requirement. You should check these PRs... I am also a 'chi' user. I need this.

chi users are waiting for a long time.

[sp-pau-tena]

@drakejin any news about when this is going to be merged?

[aleksasiriski]

Please review and merge this, it's much needed.

This is already supported? https://github.com/awslabs/aws-lambda-go-api-proxy/blob/master/chi/adapterv2.go