Support Relay GraphQL standard

# 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](https://graphql.org/learn/pagination/#complete-connection-model)
- [Global Object Identification](https://graphql.org/learn/global-object-identification/)

more details on the Relay site:

- [GraphQL Cursor Connections Specification](https://relay.dev/graphql/connections.htm)
- [GraphQL Server Specification](https://relay.dev/docs/guides/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.

Empieza revisando la sección de runtime del archivo de configuración y las especificaciones enlazadas de GraphQL y Relay para el Complete Connection Model y Global Object Identification. Se considera completado cuando una opción dedicada puede seleccionar un esquema GraphQL compatible con Relay, preservando al mismo tiempo el esquema predeterminado de Data API Builder.

Escrito por el modelo de indexación a partir del texto del issue.