Document difference from graphql-js

[IvanGoncharov]

@Cito You doing a great job keeping this lib in sync with graphql-js.
Also big thanks for taking the time to submit PRs back to graphql-js 👍

I was browsing the source code and notice that you already implemented middlewares:
https://.com/graphql-python/graphql-core-next/blob/master/graphql/execution/middleware.py

Would be great to have a list of such changes so we can figure out is it something Python specific or we should push it into graphql-js.

I also interested if you added any new tests that we can mirror in graphql-js.

[Cito]

I was actually lagging behind and trying to catch up this weekend again. Still missing the last two months of changes...

My intention for graphql-core-next was to avoid differences and additions and keep everything as close to GraphQL.js as possible. Currently there are only two additions which have been taken over from the older graphql-core for backward compatibility reasons: support for middleware and a custom execution context. You're right, these should be mentioned particularly in the docs. I'll keep this open as a reminder.

I also try to keep the test suite in sync and send PRs when I notice problems or make additions. One user contributed a test_user_registry test/demo covering mutations and subscriptions, which I have added as a top level test to the test suite, similar to the star wars test/demo.

[IvanGoncharov]

@Cito Thanks for the details.

I think we need to have middlewares in graphql-js but at the moment I'm focused more on paying the technical debt for features we already have, e.g. buildSchema/extendSchema.

BTW. I notice you don't use contain_subset anymore so it looks like you can safely delete it:
https://.com/graphql-python/graphql-core-next/search?q=contain_subset&unscoped_q=contain_subset

[Cito]

@IvanGoncharov Right, contain_subset is not needed any more after graphql/graphql-js@1d07ebf - removed it now.

[Cito]

Note to self: Document #41, #42 and overridable type_map_reducer.

[IvanGoncharov]

@Cito A little bit off-topic but why do you need overridable type_map_reducer?

[Cito]

@IvanGoncharov This is to support Graphene, a higher-level and more Pythonic library wrapping GraphQL-core. Graphene uses a custom reducer to convert its own types to the GraphQL-core types. See here for how it is used by Graphene.

[Cito]

The documentation has been added now in 2999def.