[FIX] purchase: dropshipping sequence in multi company

Usecase to reproduce:
- Create 2 sequence for PO(one for each company)
- Create a product with dropshipping
- Connect on the demo user with an active company different than the
admin company
- Create a SO for this product
It will create a PO with the admin's company sequence.

It happens because _run_buy use a sudo since SO user don't always
have the purchase and inventory rights. However the company is not
forced and thus the used company for sequence is the admin company.

opw-1860802

addons/purchase/models/purchase.py

@@ -909,7 +909,8 @@ class ProcurementRule(models.Model):
             cache[domain] = po
         if not po:
             vals = self._prepare_purchase_order(product_id, product_qty, product_uom, origin, values, partner)
-            po = self.env['purchase.order'].sudo().create(vals)
+            company_id = values.get('company_id') and values['company_id'].id or self.env.user.company_id.id
+            po = self.env['purchase.order'].with_context(force_company=company_id).sudo().create(vals)
             cache[domain] = po
         elif not po.origin or origin not in po.origin.split(', '):
             if po.origin: