Vapor 4:如何从数据透视表中包含包含额外属性的兄弟？

final class Sibling: Model {
    static let schema = "siblings"
    
    @ID(key: .id)
    var id: UUID?
    
    @Field(key: "name")
    var name: String
    
    @Field(key: "extra_property")
    var extraProperty: String
    
    init() {}
    
    init(id: UUID? = nil, name: String, extraProperty: String) {
        self.id = id
        self.name = name
        self.extraProperty = extraProperty
    }
}

final class Parent: Model {
    static let schema = "parents"
    
    @ID(key: .id)
    var id: UUID?
    
    @Field(key: "name")
    var name: String
    
    @Siblings(through: ParentSiblingPivot.self, from: \.$parent, to: \.$sibling)
    var siblings: [Sibling]
    
    init() {}
    
    init(id: UUID? = nil, name: String) {
        self.id = id
        self.name = name
    }
}

final class ParentSiblingPivot: Model {
    static let schema = "parent_sibling_pivot"
    
    @ID(key: .id)
    var id: UUID?
    
    @Parent(key: "parent_id")
    var parent: Parent
    
    @Parent(key: "sibling_id")
    var sibling: Sibling
    
    init() {}
    
    init(id: UUID? = nil, parentID: Parent.IDValue, siblingID: Sibling.IDValue) {
        self.id = id
        self.$parent.id = parentID
        self.$sibling.id = siblingID
    }
}

let parent = Parent.query(on: req.db)
    .filter(\.$name == "John")
    .with(\.$siblings)
    .first()
    .flatMap { parent in
        guard let parent = parent else {
            throw Abort(.notFound)
        }
        
        let siblings = parent.siblings.map { sibling in
            return (sibling.name, sibling.extraProperty)
        }
        
        return req.eventLoop.makeSucceededFuture(siblings)
    }