[FIX] web_editor: type of res_id

- Set the demo user to have access to all quotations
- Connect as demo, create a quote and send the message
- In the message try to upload an image

An access error is raised, although the user can write on the record.

This is because the `res_id` received is a `string`, not an `int`.
Therefore, the access check fails.

Introduced with 6494f51

opw-1824673

addons/web_editor/controllers/main.py

@@ -147,7 +147,10 @@ def attach(self, func, upload=None, url=None, disable_optimization=None, **kwarg
         Attachments = request.env['ir.attachment']  # registry for the attachment table
 
         res_model = kwargs.get('res_model', 'ir.ui.view')
-        res_id = res_model != 'ir.ui.view' and kwargs.get('res_id') or None
+        if res_model != 'ir.ui.view' and kwargs.get('res_id'):
+            res_id = int(kwargs['res_id'])
+        else:
+            None
 
         uploads = []
         message = None