Product Form Sale Link

This module makes it easy to jump from a product to the sales history of that product.

• On both the product template form and the product variant form, a new "Sales" stat button appears in the button box. It shows a count of sale order lines for that product.
• The button is only visible for users in the Sales / Salesman group and only when the product is marked as sellable (sale_ok).
• Clicking the button opens a list of sale order lines filtered to that product (or to all variants of the template). The list is pre-filtered to show only confirmed sales orders and done orders.
• The count is computed automatically: it counts sale order lines whose status is "Sales Order" or "Done", limited to the companies the current user is allowed to see. If the user is not a salesman, the count is zero.
• On the sale order line list view, two new filters are added: "Quotations" (draft and sent) and "Sales Orders" (sale and done), making it quicker to separate quotes from confirmed orders.

The module touches product.product, product.template and sale.order.line, and adds a window action named "Sale Order Lines".