GraphQL schema for federated service extending saleor

schema.graphql

type User @key(fields: "id") @extends {
    id: ID! @external
    reviews: [Review]
}

type Review @key(fields: "id") {
    id: ID!
    title: String
    author: User
}

type Query @extends {
    reviews: [Review!]!
}

type Mutation @extends {
    addReview: Review
}