Need help re DGraph+Federation - how to avoid Filter and Ref types on external types?

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UPDATE: Seems related to or same as Cannot Use Apollo Federation with Multiple Dgraph Instances

I am evaluating DGraph for a small service, PoC at this point, that will need to participate in Apollo Federation. Right now it has only one own type and refers to another from another service:

type ExternalContainer 
@key(fields: "id") @extends
@generate(query: { get: false, query: false, aggregate: false }, mutation: { add: false, update: false, delete: false}, subscription: false)
{
  id: ID! @external
  myItems: [MyItem!]!
}

type MyItem @key(fields: "id") {
  id: ID!
  container: ExternalContainer!
  ...
}

Generation of supergraph fails:

    UNKNOWN: The `ExternalContainerHasFilter` enum does not have identical values in all services. Groups of services with identical values are: [mine], [externalContainer]
    UNKNOWN: The `ExternalContainerOrderable` enum does not have identical values in all services. Groups of services with identical values are: [mine], [externalContainer]
    UNKNOWN: Field "ExternalContainerAggregateResult.count" can only be defined once.
    UNKNOWN: There can be only one type named "ExternalContainerAggregateResult".
    UNKNOWN: Field "ExternalContainerHasFilter.id" can only be defined once.
    UNKNOWN: Field "ExternalContainerHasFilter.has" can only be defined once.
    UNKNOWN: Field "ExternalContainerHasFilter.and" can only be defined once.
    UNKNOWN: Field "ExternalContainerHasFilter.or" can only be defined once.
    UNKNOWN: Field "ExternalContainerHasFilter.not" can only be defined once.
    UNKNOWN: There can be only one type named "ExternalContainerHasFilter".
    UNKNOWN: Field "ExternalContainerRef.id" can only be defined once.
    UNKNOWN: There can be only one type named "ExternalContainerRef".

How do I tell DGraph to not generate these types at all in that way? With respect to MyItem.container I need this to only store the id of ExternalContainer as well.

Please help.