CartController::add_to_cart()
Method: Based on the core cart class but returns errors rather than rendering notices directly.
Source: woocommerce/packages/woocommerce-blocks/src/RestApi/StoreApi/Utilities/CartController.php:32
CartController::get_cart_instance()
Method: Get main instance of cart class.
Source: woocommerce/packages/woocommerce-blocks/src/RestApi/StoreApi/Utilities/CartController.php:128