Odoo - Add a validation rule when a product is saved after editing.

Odoo - Add a validation when a table is saved. User Story: as an admin user when I save a "product" after editing, it should check if the product has already got orders or not. If the product has existing orders, the "Product type" field should not be allowed to change. If it is changed during my editing, there should be an error message preventing the saving of the record. Technical Requirements: Please write a custom module for this function. Or you can do it by a configuration , but the configuraiton has to be exportable and loadable into other odoo instances. How to work: Please develop this module your own odoo 11 community eidition environment and test it. Then you push your module to github repo for my testing and acceptance. If you do it by configuraiton, please develop it on your own odoo11 communicty edition and export your configuraiton and upload into my odoo instance for my testing and acceptance. How to bid: please specify the time & cost for this task Prefer someone who can work today or tomorrow