Odoo V10e

We use Analytic accounts as Order Types.
I would like to add/append a tag based on what order type(s) customers have done.

Basically, once the Sales Order is entered and saved it would add whatever order type customer tag that matches the analytic account. So if the Analytic tag on the Sales Order was "Repair Parts" it would set "Repair Parts" tag to the customer.

Then in the contacts screen, you could filter by tag "Repair Parts" and easily tell what customers have placed an order with the analytic account of "Repair Parts". Same would go for any other order type name we would have.

Also, If there are other tags already applied to the customer It should keep them and not overwrite them.

How would you go about doing this through an automated server action?