我正在使用Apollo联邦，当尝试创建类似于计算字段的内容时遇到错误（https：//www.apollographql.com/docs/federation/entities/# extending-an-entity-with-computed-fields-advanced）：

Error: A valid schema couldn't be composed. The following composition errors were found:client-api-gateway_1
[Payments MS] User.parentId -> marked @external but parentId is not defined on the base service of User (Users MS)

我有两项服务：Users和Payments。在users服务中，i存储关于用户的信息，并且在payments中，存储关于连接到用户的支付的信息。
Users服务图：

type User @key(fields: "id") {
        id: Int!
        name: String!
        surname: String!
        type: USER_TYPE!
        parentId: Int
    }

Payments服务图：

type UserSubscriptionInfo {
     nextChargeAmount: Int
     ......etc
}

extend type User @key(fields: "id") {
     id: Int! @external
     parentId: Int @external
     subscription: UserSubscriptionInfo @requires(fields: "parentId")
}

基于用户类型parentId，我希望通过扩展User类型获得订阅。