Also fetch in_stock when stock_status requested in V2.

When called from V3, controller calls V2s get_product_data method, where stock_status was did not existed and was renamed. In V3 controller, we compute it based on V2 in_stock field.

includes/rest-api/Controllers/Version2/class-wc-rest-orders-v2-controller.php

@@ -293,6 +293,7 @@ class WC_REST_Orders_V2_Controller extends WC_REST_CRUD_Controller {
 					$data['coupon_lines'] = $order->get_items( 'coupon' );
 					break;
 				case 'refunds':
+					$data['refunds'] = array();
 					foreach ( $order->get_refunds() as $refund ) {
 						$data['refunds'][] = array(
 							'id'     => $refund->get_id(),

includes/rest-api/Controllers/Version2/class-wc-rest-products-v2-controller.php

@@ -753,6 +753,7 @@ class WC_REST_Products_V2_Controller extends WC_REST_CRUD_Controller {
 				case 'stock_quantity':
 					$base_data['stock_quantity'] = $product->get_stock_quantity( $context );
 					break;
+				case 'stock_status': // For API V3, this field is computed using `in_stock`.
 				case 'in_stock':
 					$base_data['in_stock'] = $product->is_in_stock();
 					break;