[MIG] website_blog: new api migration

- Task: https://www.odoo.com/web?debug=#id=9783&view_type=form&model=project.task&action=333&active_id=131
- Pad: https://pad.odoo.com/p/r.gSXNQBNaLZL5Ausm
I think you should keep the count=count and pass the ids to the method. By the way, I think _get_discussion_detail should read the messages with some given fields. Reconstruct an ordered list based on ids + read result to pass to Qweb.