[FIX] website_forum: error when converting answer/comment

- Create 2 companies (A and B for instance);
- Create 2 users with password, one on each company (user 'a' in
  company A and user 'b' in company B);
- Add enough karma on both users;
- Add a valid email address to both users;
- As user 'b' :
  - open any forum topic and validate the email address;
  - post an answer or comment to a forum post;
- As user 'a' :
  - open the forum and find the answer/comment made by user 'b';
  - convert the answer as comment or convert a comment as answer;

Before this commit, an error was raised : 'Access to unauthorized or
invalid companies'.

opw-2296470

closes odoo/odoo#55301

X-original-commit: ce63a20ca26f1773ea7e1133b0a3796fda692e11
Signed-off-by: Jorge Pinna Puissant (jpp) <jpp@odoo.com>

addons/website_forum/models/forum.py

@@ -780,7 +780,7 @@ class Post(models.Model):
             'date': self.create_date,
         }
         # done with the author user to have create_uid correctly set
-        new_message = question.with_user(self_sudo.create_uid.id).with_context(mail_create_nosubscribe=True).message_post(**values)
+        new_message = question.with_user(self_sudo.create_uid.id).with_context(mail_create_nosubscribe=True).sudo().message_post(**values).sudo(False)
 
         # unlink the original answer, using SUPERUSER_ID to avoid karma issues
         self.sudo().unlink()
@@ -824,7 +824,7 @@ class Post(models.Model):
             'name': _('Re: %s') % (question.name or ''),
         }
         # done with the author user to have create_uid correctly set
-        new_post = self.with_user(post_create_uid).create(post_values)
+        new_post = self.with_user(post_create_uid).sudo().create(post_values).sudo(False)
 
         # delete comment
         comment.unlink()