Complex @Property Types

Could anyone point towards documentation or an example of more complex types? I'm working on migrating a complex Shopping Cart which I would like to assign sub-document ObjectIDs or some other unique identifier at the scope of the user's cart. An example i'm trying to model for below. 1.) Not sure the best way to handle an object that could be one of two types. 2.) how to specify sub document ObjectIds. 3.) I Imagine for the Endpoint denormalization i have on the line items I will have to just make a constant for that.

export class Cart {
    constructor(
        private userId: string,
        private dateCreated: string,
        private lineItems: Array<CartLineItem>,
        private _id?: string,
    ) { }
...
}

export class CartLineItem {
    constructor(
        private type: string,
        private keys: IndexedItemKeys | ArchivedItemKeys,
        private endpoint: Endpoint,
        private pages: number[],
        private description: string,
        private cost?: number,
        private _id?: string
    ) { }
}

export class IndexedItemKeys {
    constructor(
        private instrument: string,
        private documentName: string
    ) { }
}

export class ArchivedItemKeys {
    constructor(
        private bookReference: string,
        private bookNumber: string,
        private bookSuffix: string,
        private pageNumber: string,
        private pageSuffix: string
    ) { }

}
export class Endpoint {
    constructor(
        private stateId: number,
        private countyId: number,
        private stateAbbrevation: string,
        private url: string,
        private name: string,
        private status: number,
        private hasCreditModule: boolean,
        private hasArchiveModule: boolean,
        private _id?: string,
    ) { }
...
}
// Iridium Schema
@Collection('carts')
export class CartMongoSchema extends Instance<CartDTO, CartMongoSchema> {
    @ObjectID
    _id: string;
    @ObjectID
    userId: string;
    @ObjectID
    endpointId: string;
    @Property(Date)
    dateCreated: Date;
    @Property({
        $required: false,
        $type: [{
            type: String,
            // Not sure best way to handles these as depicted in class above can be of either type
            keys: Object,
            // is an entity from another collection and has an ObjectID.
           // intentional de-normalization.
            endpoint: Object,

            pages: [Number],
            description: String,
            cost: Number,
        }]})
    lineItems: Array<CartLineItem>;
}

SierraSoftworks / Iridium

Complex @Property Types #97