Fix dynamic property creation warning in `class-woocommerce.php` (#36545)

Declares $api as a public property to the WooCommerce class in order to avoid a deprecation warning that will eventually be an error in upcoming PHP versions.

plugins/woocommerce/changelog/fix-35763-dynamic-property-creation-in-woocommerce-class

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Define a public `api` property in the WooCommerce class to prevent a PHP deprecation warning

plugins/woocommerce/includes/class-woocommerce.php

@@ -65,6 +65,13 @@ final class WooCommerce {
 	 */
 	public $query = null;
 
+	/**
+	 * API instance
+	 *
+	 * @var WC_API
+	 */
+	public $api;
+
 	/**
 	 * Product factory instance.
 	 *

plugins/woocommerce/tests/php/includes/class-woocommerce-test.php

@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * Unit tests for the WooCommerce class.
+ */
+class WooCommerce_Test extends \WC_Unit_Test_Case {
+
+	/**
+	 * Test that the $api property is defined, public and initialized correctly.
+	 */
+	public function test_api_property(): void {
+		$property = new ReflectionProperty( WooCommerce::class, 'api' );
+
+		$this->assertTrue( $property->isPublic() );
+		$this->assertInstanceOf( WC_API::class, $property->getValue( WC() ) );
+	}
+}