[FIX] purchase: Drop shipping with no access to Purchase

Let's consider a Sales user U with no access to Purhcase

Steps to reproduce the bug:
- Create a SO with one line with the drop shipping route
- Validate the SO

Bug:

 A access error was raised because the user has no access right on
Purchase.

opw:1851301

addons/purchase/models/purchase.py

@@ -904,12 +904,12 @@ class ProcurementRule(models.Model):
         if domain in cache:
             po = cache[domain]
         else:
-            po = self.env['purchase.order'].search([dom for dom in domain])
+            po = self.env['purchase.order'].sudo().search([dom for dom in domain])
             po = po[0] if po else False
             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'].create(vals)
+            po = self.env['purchase.order'].sudo().create(vals)
             cache[domain] = po
         elif not po.origin or origin not in po.origin.split(', '):
             if po.origin:
@@ -930,7 +930,7 @@ class ProcurementRule(models.Model):
                     break
         if not po_line:
             vals = self._prepare_purchase_order_line(product_id, product_qty, product_uom, values, po, supplier)
-            self.env['purchase.order.line'].create(vals)
+            self.env['purchase.order.line'].sudo().create(vals)
 
     def _get_purchase_schedule_date(self, values):
         """Return the datetime value to use as Schedule Date (``date_planned``) for the