[MIGRATED] website_forum: migrated website_forum into new api + solved s...

...ome bugs

[IMP] website_forum: removed unnecessary imports
[IMP] website_forum: improved badges access for anonymous user
[IMP] wesite_forum: bug solved for ckeditor

- Task: https://www.odoo.com/web?&debug=#id=9031&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.4HSUoPQ9tBfdQEdN
Beware: search() returns a recordset in the new API.