[IMP]mass_mailing module in campaign is created go to form view in add g...

...et stat button with the number of mailings and mass_mailing_ids (one2many) field in add a base.group_no_one.

- Task: https://www.odoo.com/web#id=9833&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.rYaZxxlRhq1AGlP8