[FIX] website: get right access token for public visitor user

Current Behavior:

When we get the access token for a website visitor, we check if the
`self.env.user` is a public user. If it is, we return his id.

Expected behavior:

We should check the `request.env.user` instead since the visitor can
only be created through the frontend.

opw-2956186

Part-of: odoo/odoo#99181

addons/website/models/website_visitor.py

@@ -37,8 +37,8 @@ class WebsiteVisitor(models.Model):
         if not request:
             raise ValueError("Visitors can only be created through the frontend.")
 
-        if not self.env.user._is_public():
-            return self.env.user.partner_id.id
+        if not request.env.user._is_public():
+            return request.env.user.partner_id.id
 
         msg = repr((
             request.httprequest.remote_addr,