[FIX] website_sale_digital : fix AccessError attachment

A user get a AccessError during a valid flow on the website shop
due to a attachment search (with website_sale_digital installed) :
- As a portal user buy a product and pay with wire tranfer (or other)
- Check the your quotation with this user and we get a AccessError
for the read ir.attachment model.

The bug comes from the website_sale_digital module which add a search
on ir.attachment for each product (allows digital product sell,
eg. ebook) on the controller rendering orders. To fix this issue, add
a sudo call before the search. It is legit because only the name and
date is retrieved and the download (of the digital product) checks
the access of this product attachment (if user already paid for it).

TASK_ID : 2004031

closes odoo/odoo#39000

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

addons/website_sale_digital/controllers/main.py

@@ -49,7 +49,7 @@ class WebsiteSaleDigital(CustomerPortal):
             Attachment = request.env['ir.attachment']
             product_id = product.id
             template = product.product_tmpl_id
-            att = Attachment.search_read(
+            att = Attachment.sudo().search_read(
                 domain=['|', '&', ('res_model', '=', product._name), ('res_id', '=', product_id), '&', ('res_model', '=', template._name), ('res_id', '=', template.id), ('product_downloadable', '=', True)],
                 fields=['name', 'write_date'],
                 order='write_date desc',