async register(email, password, isAgreed, voucher) {
    try {
        const user = await UserService.register(email, password, isAgreed);
        await Promise.all([
            CustomerService.create(user._id),
            EmailService.sendWelcomeEmail(email),
            MailChimpService.register(email),
            VoucherService.applyVoucher(user._id, voucher),
]);
        return {
            token: user.token,
        }
    } catch (err) {
        throw err;
    }
}