Add next_sched_contribution_date as subscription parameter for getObjectParam

CRM/Stripe/Api.php

@@ -168,6 +168,9 @@ class CRM_Stripe_Api {
           case 'cancel_date':
             return self::formatDate($stripeObject->canceled_at);
 
+          case 'next_sched_contribution_date':
+            return self::formatDate($stripeObject->current_period_end);
+
           case 'cycle_day':
             return date("d", $stripeObject->billing_cycle_anchor);