Support rover supergraph fetch for contract variants

[lennyburdette]

From a customer:

When using rover supergraph fetch <variant_graph_ref> it fails saying:

error[E007]: The graph `customer@contract-variant` is a non-federated graph. This operation is only possible for federated graphs.
        Try running the command on a valid federated graph, or use the appropriate `rover graph` command instead of `rover subgraph`.

The use case is fetching the supergraph schema to use in an Uplink fallback. They need the contract supergraph with all the @inaccessible directives applied.

@jsegaran and @david-castaneda are working on an API change that should make this possible.

[abernix]

I can confirm that our remote API doesn't yet support contract variants! Once that lands, this will just start working right? With no changes on Rover?

[david-castaneda]

@lennyburdette @abernix The API for fetching the latest approved schema should be ready for use.

This query should work for regular variants and contract variants.

query {
  service(id: "") {
    variant(name: "") {
      latestApprovedLaunch {
        build {
          result {
            ... on BuildSuccess {
              coreSchema {
                apiDocument
                coreDocument
              }
            }
          }
        }
      }
    }
  }
}

[EverlastingBugstopper]

hey @david-castaneda - would love to accept a PR that uses this new query!

[lennyburdette]

@david-castaneda will latestApprovedLaunch always be a successful launch?

[jsegaran]

Yep. The latest approved launch contains the schema that is being used by uplink for running gateways/routers.

[jsegaran]

Yep. The latest approved launch contains the schema that is being used by uplink for running gateways/routers.

[EverlastingBugstopper]

This works now.