I am developing an application using WooCommerce rest API v3. Now I'm trying to integrate coupons from my WooCommerce website to my application. I'm creating order and applying coupons like this
"coupon_lines":[{
    'code'=>'coupon1',
    'amount'=>'1.00'
}]
I've set a usage limit per user in woocommerce website.
When I ordered directly from the website, usage restrictions are applied correctly. i.e, a user cannot use a coupon when a limit is reached. But when I make an order via REST API, the restrictions are not applied.
Additionally, I got a reply from another forum stating that coupon apply feature is not yet available via rest API. But, while looking through the code of create_order API endpoint, I found that the webhook for applying coupon is called there. 
 do_action( 'woocommerce_order_add_coupon', $this->id, $item_id, $code, $discount_amount, $discount_amount_tax ); 
in add_coupon(). But I didn't find the add_action('woocommerce_order_add_coupon',...) . Can anyone tell me where should I write this action definition so that it shouldn't get overwritten when updating WooCommerce?
 
     
     
    