product_usability: seller_id can not be store as muti-company will be…

… broken

do not store the field as shared product can have different supplier
depending on the company logged
Use compute as related will always pick the first one whatever the
company logged

product_usability/models/product_template.py

@@ -14,7 +14,8 @@ class ProductTemplate(models.Model):
     # in v10, that field was defined in procurement_suggest, but we will
     # probably not port procurement_suggest because it is native in v14
     seller_id = fields.Many2one(
-        'res.partner', related='seller_ids.name', store=True,
+        'res.partner',
+        compute="_compute_seller_id",
         string='Main Supplier')
 
     # in v14, I noticed that the tracking of the fields of product.template
@@ -33,6 +34,10 @@ class ProductTemplate(models.Model):
     company_id = fields.Many2one(tracking=110)
     barcode_type = fields.Char(compute='_compute_template_barcode_type')
 
+    def _compute_seller_id(self):
+        for record in self:
+            record.seller_id = fields.first(record.seller_ids).name
+
     @api.depends('product_variant_ids.barcode')
     def _compute_template_barcode_type(self):
         ppo = self.env['product.product']