[IMP] product_usability: forward-port seller_id now a computed field with search method

stock_usability: Add seller_id on orderpoints.

stock_usability/models/stock_warehouse_orderpoint.py

@@ -15,6 +15,23 @@ class StockWarehouseOrderpoint(models.Model):
     # but all the Odoo deployments I've seen so far need 'manual' by default
     trigger = fields.Selection(default='manual')
     product_barcode = fields.Char(related='product_id.barcode', string="Product Barcode")
+    seller_id = fields.Many2one(
+        "res.partner",
+        compute="_compute_seller_id",
+        search="_search_seller_id",
+        string="Main Supplier")
+
+    def _search_seller_id(self, operator, value):
+        # searching on the first line of a o2m is not that easy
+        # So we search all potential matching products
+        # Then we filter on the seller_id
+        records = self.search([("product_id.seller_ids.partner_id", operator, value)])
+        records = records.filtered_domain([("seller_id", operator, value)])
+        return [("id", "in", records.ids)]
+
+    def _compute_seller_id(self):
+        for orderpoint in self:
+            orderpoint.seller_id = fields.first(orderpoint.product_id.seller_ids).partner_id
 
     def _procure_orderpoint_confirm(
             self, use_new_cursor=False, company_id=None, raise_user_error=True):