KoaJS integration

[leandroruel]

Goals

1. Add KoaJS integration since there's a express integration.
2. Docs: Add tutorial How to integrate Auth using koa/middleware and apollo (optional)
3. Add a folder with examples in the repo

Non-Goals

Background

i've been building a authorization and permissions api with graphql-shield and graphql-middleware but both are outdated, with a lot of issues open and people questioning if they are abandoned, also i tried other alternatives and they all seem like make a lot of code and not have a huge community like Authjs, i'm trying to find a good lib like this one but for Koa. unfortunelly there's no integration yet.

Proposal

i still not have intention to contribute yet due to a massive amount of work on my job