[RFR] Support for inline fragments for GraphQL Interfaces

[MichielDeMey]

This PR adds improved support for GraphQL Interface types.

For example if you have the following schema:

interface Device {
  prop1
}

type MotionSensor implements Device {
  prop2
}

type TemperatureSensor implements Device {
  prop3
}

It will now generate the correct inline fragments for the interface when building the GraphQL query.

devices {
  ... on MotionSensor {
    prop1
    prop2
  }
  ... on TemperatureSensor {
    prop1
    prop3
  }
  prop1
}

Allowing you to get prop2 and prop3 from the resource in react-admin.

<TextField source="prop1" />
<TextField source="prop2" />
<TextField source="prop3" />

Note: Requires #3692 and #3712 to be merged

[fzaninotto]

New features should be PRed against the next branch, can you please rebase?

[djhi]

It needs rebase because #3712 has been merged

[djhi]

@fzaninotto I think this can be merged on master. It's not really a new feature but a better support for existing things in GQL

[fzaninotto]

Fine, let's merge it on master once it's rebased.

[MichielDeMey]

PR rebased to master now. 👍

[fzaninotto]

but tests fail...

[MichielDeMey]

Tests have been fixed :)

[djhi]

Thanks!