Add an example using Nexus to extend the Keystone schema

[JedWatson]

This came up on Slack, and I was interested in testing out how to use Nexus to extend Keystone's GraphQL API. So I wrote up this example.

Turns out it's pretty neat, although there are a couple of limitations that we could improve in the future:

• Nexus really wants you to run a watch process while you're coding, to regenerate types as you work. Since Keystone doesn't do hot reloading at the moment, I've added a dev-nexus script which is completely hacky but gets the job done. not a problem anymore with the live reloading in Keystone now
• You can't use Keystone's GraphQL types in Nexus, it should be totally possible but I haven't worked out how to make Nexus aware of the GraphQL schema Keystone generates yet
• Nexus also has a Prisma plugin, which simplifies type definition. We should be able to get Nexus in this example hooked up to the Prisma schema that Keystone generates

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[JedWatson]

Note on the status of the Prisma plugin:

I just read through graphql-nexus/nexus-plugin-prisma#1039 and it's being rewritten, the one you can use today only works with an older version of Prisma than the one that Keystone uses so we should definitely wait for the new one (here) is ready for use.

[bladey]

Nice example.

Getting the following when running yarn dev and/or yarn dev-nexus (doesn't matter the combination), regardless it all seems to work still:

When attempting to request nexusPosts:

Aren't dates supposed to be ISO Strings?

Works if changed to toISOString() and having a post with a publish date being in the future:

For the things example, I can't pull out:

  things {
    id
    title
  }

Based on what the data looks like:

As there is a mismatch here:

Changing this on the fly it gets detected as a change:

But still fails to resolve until I restart Keystone itself:

After a restart:

[bladey]

Works well.