Hi, I am looking for third party app that will give me the option to add purchase discount. 

This discount should reflect on product cost. For example: If I order product at price of 100€ and add 10% discount for it on purchase order it's cost will be 90€. I need to show 90€ as cost on product form, not 100€. 

This is implemented in Odoo 17 by default but we need it in version 16. Any suggestions for app that can do it?