feat(Relay::Node) allow passing a custom resolver to the node and nod…

[xuorig]

…es fields

Context:

Wanted to batch the node and nodes field which requires you to return a lazy object in object_from_id

If you do that, by default the nodes field would return an array of promises / lazy things [Promise, Promise, Promise].

Of course, graphql-ruby cant magically guess this is an array of lazy objects, and not all implementations have something like Promise.all([...]) so that would be hard to add.

With this PR this would allow somebody to override the default resolve when something like this:

GraphQL::Relay::Node.plural_field(
  resolve: ->(_, args, ctx) { Promise.all(args[:ids].map { |id| ctx.query.schema.object_from_id(id, ctx) }) }
)

[rmosolgo]

Awesome! For some reason I thought that was already possible but obviously not!

I'll merge this as-is but a long-term win would be to accept any definition from those methods, something like

def field(**kwargs, &block)
  node_field = GraphQL::Field.define { 
    # ... existing definition here 
  }
  # Then apply user-specified overrides:
  node_field.redefine(kwargs, &block)
end 

[xuorig]

Great idea @rmosolgo, I've implemented it here: #552