Master event kanban ppa

- Task: https://www.odoo.com/web?&debug=#id=8708&view_type=form&model=project.task&action=333&active_id=131
- Pad: https://pad.odoo.com/p/r.4ziC9amJvS5GLIcm
Isn't it possible to do the read_group on all event_ids, then group on event_id and create_date, using lazy=False to do all queries in on call ?