Support Relay GraphQL standard

[yorek]

Summary

Add support for the Relay GraphQL standard

Motivation

Relay provides quite a lot of useful features to front-developers and given that fact that it is almost a de-facto standard, it means many libraries can provide implementation so that its usage can be ever easier. This is expected to drive adoption of tools like DAB.

Functional Specifications

Relay is based on two core GraphQL "best practitices" that needs to be implemented in order to support Relay:

• Complete Connection Model
• Global Object Identification

more details on the Relay site:

• GraphQL Cursor Connections Specification
• GraphQL Server Specification

It should be possible to decide if to generate a Relay-compatible GraphQL schema or use the default one provided by Data API Builder, but setting a dedicated configuration option (in the runtime section) in the configuration file.

[alloy]

An important part of this will be to stop referring to it as something that is for Relay. These are best-practices for any application/client that uses GraphQL as per its original data-driven UI intent.