Ensure payment has captured before setting order's payment as complete (#2224)

Before, even if Stripe had not captured the payment, the plugin would
set the order's payment as complete. Now, we ensure that the payment
has been captured by Stripe, before setting the order's payment status
as complete.

Author: lovo-h

includes/class-wc-stripe-webhook-handler.php

@@ -439,6 +439,14 @@ public function process_webhook_charge_succeeded( $notification ) {
 			return;
 		}
 
+		// When the plugin's "Issue an authorization on checkout, and capture later"
+		// setting is enabled, Stripe API still sends a "charge.succeeded" webhook but
+		// the payment has not been captured, yet. This ensures that the payment has been
+		// captured, before completing the payment.
+		if ( ! $notification->data->object->captured ) {
+			return;
+		}
+
 		// Store other data such as fees
 		$order->set_transaction_id( $notification->data->object->id );