TypeORM一对一关系，其中特定值匹配

Question

我有两个实体，促销：

@Entity()
export class Promotion extends BaseEntity {

    @PrimaryColumn()
    public id: number;

    @Column()
    public title: string;

    @Column()
    public ean: string;

    @Column()
    public discountPrice: string;

    @Column()
    public validUntil: Date;

}

和产品：

@Entity()
export class Product extends BaseEntity {

    @PrimaryColumn()
    public id: number;

    @Column()
    public ean: string;

    @Column()
    public title: string;

    @Column()
    public brand: string;

    @Column({ nullable: true })
    public shortdescription: string;

    @Column({ nullable: true })
    public fulldescription: string;

    @Column()
    public image: string;

    @Column()
    public weight: string;

    @Column()
    public price: string;

    @Column()
    public category: string;

    @Column()
    public subcategory: string;

    @Column()
    public subsubcategory: string;

    @OneToOne((_) => Promotion, (promotion) => promotion.ean)
    @JoinColumn()
    public promotion: Promotion;

}

我将数据保存在单独的文件中，因为我是从api中获取数据的，现在我想让TypeORM在产品表中设置外键PromotionId以匹配ean匹配的行的ID，我该怎么办？