Свяжите модель подписки с моделью пользователя

У меня есть настройки Stripe и PayPal по модели подписки. Мне нужна помощь в понимании того, как создать связь между подпиской и моделью пользователей.

Любая помощь в этом будет принята с благодарностью.

Модель подписки:

    belongs_to :plan
      validates_presence_of :plan_id
      validates_presence_of :email

      attr_accessor :stripe_card_token, :paypal_payment_token

      def save_with_payment
        if valid?
          if paypal_payment_token.present?
            save_with_paypal_payment
          else
            save_with_stripe_payment
          end
        end
      end

      def paypal
        PaypalPayment.new(self)
      end

      def save_with_paypal_payment
        response = paypal.make_recurring
        self.paypal_recurring_profile_token = response.profile_id
        save!
      end

      def save_with_stripe_payment
        customer = Stripe::Customer.create(description: email, plan: plan_id, card: stripe_card_token)
        self.stripe_customer_token = customer.id
        save!
      rescue Stripe::InvalidRequestError => e
        logger.error "Stripe error while creating customer: #{e.message}"
        errors.add :base, "There was a problem with your credit card."
        false
      end

      def payment_provided?
        stripe_card_token.present? || paypal_payment_token.present?
      end

  def cancel_recurring
     response = ppr.cancel_subscription(at_date_end: true)
     self.current_date_end_at = Time.at(response.current_date_end)
     self.plan_id = plan.id
     self.status = "canceled"
     return self.save
   end
    end