Swift Vapor 4，如何按外键过滤

我有两个模型(UserModel和用户令牌模型)

用户令牌模型有一个指示UserModel的ForeignKey.

这是我的密码.我试图在用户令牌模型上按userModel的Id进行筛选，但出现了一个错误.

运算符函数"=="要求"UUID"符合"QueryableProperty"

if let user = try await UserModel.query(on: req.db).filter(\.$email == request.email).first() {
    //Compile Error: 运算符函数"=="要求"UUID"符合"QueryableProperty"
    let userToken = try await 用户令牌模型.query(on: req.db)
    .filter(\.$user.id == user.$id).first()
}

以下是模型的定义

final class UserModel: Model {
    static let schema = "user_users"
    
    struct FieldKeys {
        static var email: FieldKey { "email" }
        static var password: FieldKey { "password" }
        static var appleId: FieldKey { "appleId" }
        static var givenName: FieldKey { "givenName" }
        static var familyName: FieldKey { "familyName" }
        static var userName: FieldKey { "userName" }
    }
    
    //MARK:- fields
    @ID() var id: UUID?
    @Field(key: FieldKeys.email) var email: String
    @Field(key: FieldKeys.password) var password: String
    @Field(key: FieldKeys.appleId) var appleId: String?
    @Field(key: FieldKeys.givenName) var givenName: String?
    @Field(key: FieldKeys.familyName) var familyName: String?
    @Field(key: FieldKeys.userName) var userName: String?
    
    init() {}
    
    init(id: UserModel.IDValue? = nil,
         email: String,
         password: String,
         appleId: String? = nil,
         givenName: String? = nil,
         familyName: String? = nil,
         userName: String? = nil
    ) {
        self.id = id
        self.email = email
        self.password = password
        self.appleId = appleId
        self.givenName = givenName
        self.familyName = familyName
        self.userName = userName
    }
}

用户令牌模型

final class 用户令牌模型: Model {
    static let schema = "user_tokens"
    
    struct FieldKeys {
        static var value: FieldKey { "value" }
        static var userId: FieldKey { "user_id" }
    }
    
    //MARK:- fields
    
    @ID() var id: UUID?
    @Field(key: FieldKeys.value) var value: String
    @Parent(key: FieldKeys.userId) var user: UserModel
    
    init() {}
    init(
        id: 用户令牌模型.IDValue? = nil,
        value: String,
        userId: UserModel.IDValue
    ) {
        self.id = id
        self.value = value
        $user.id = userId
    }
}