Describe the bug
REST Api do not show variations / grouped_products IDs like the WooCommerce API on GET of product (parent).

To Reproduce
Steps to reproduce the behavior:

1. Create a variable product
2. Request product on API.

curl --location --request GET 'https://example.com/wp-json/dokan/v1/products/99' \

Expected behavior
Show values on 'variations' and 'grouped_products'.

Environment (please complete the following information):

• Dokan Version: master
• Dokan Pro Version: none
• WooCommerce Version: 5.5.1