Error with Multiple Coupons

Hi there!

Great Plugin. I noticed an issue when there are multiple subscriptions. The before_calculate_cart_total function creates an error because it only checks for the first [0] coupon in cart. I have fixed this with the following code:

    /**
     * Update cart data with coupon trial length & trial period before calculating cart data
     * 
     * @param $cart
     */
   
    public function before_caculate_cart_total($cart)
    {   
            
        if($cart->get_applied_coupons())
        {
            // Get Coupon id

            $coupon_ids = $cart->get_applied_coupons();

            foreach ($coupon_ids as $coupon_id) {
                $coupon = new WC_Coupon( $coupon_id );
                
                if($coupon->is_type('subscription_trial'))
                {

                    $coupon_trial_length = $coupon->get_meta('_wcsc_coupon_trial_length');
                    $coupon_trial_period = $coupon->get_meta('_wcsc_coupon_trial_period');

                    // Check if the coupon apply
                    if($coupon_trial_length>0)
                    {                            
                        foreach( $cart->cart_contents as $cart_item_id=>$cart_item ) 
                        {

                            if(is_a($cart_item['data'], 'WC_Product_Subscription') || is_a($cart_item['data'], 'WC_Product_Subscription_Variation'))
                            {
                                $cart_item['data']->update_meta_data('_subscription_trial_length', $coupon_trial_length, true);
                                $cart_item['data']->update_meta_data('_subscription_trial_period', $coupon_trial_period, true);
                            }
                        }
                    }
                }

            }

        }
    }