[FIX] website_sale: add the parameter _mail_post_access on product.template

This parameter gives the possibility to post messages en product.template to
people having a read access. The website_sale giving the possibility to post
comments, people not belonging to the 'Sale Manager' group were not able to
post messages.

addons/website_sale/models/product.py

@@ -33,6 +33,7 @@ class product_template(osv.Model):
     _inherit = ["product.template", "website.seo.metadata"]
     _order = 'website_published desc, website_sequence desc, name'
     _name = 'product.template'
+    _mail_post_access = 'read'
 
     def _website_url(self, cr, uid, ids, field_name, arg, context=None):
         res = dict.fromkeys(ids, '')