onchange->depends because price change was not triggering update on prod.financing

Change the decorator on meth on_change_financing to be a depends and redefine field quota_amount as computed so as when the price is changed either in db or by ui this meth is triggered and update the product.financing recordsets properly.

quota_amount field must be editable.

We better leave the onchange method as now and we could add a new button to recompute the quota_amount field.

closed