Assert uniqueness of Primary Column values

[GregBrimble]

Nothing currently stopping you from doing:

@Entity({ datastore })
class User {
    @Column({ isPrimary: true })
    public id: string

    @Column()
    public name: string

    constructor(id, name) {
        this.id = id
        this.name = name
    }
}

const userRepository = getRepository(User)

const instance = new User('123', 'Jack')
await userRepository.save(instance)

const otherInstance = new User('123', 'Jill')
await userRepository.save(otherInstance)