Base issue: unnecessary inherit of composer on mail.message. Indeed there are
a lot of unused fields coming from mail.message as well as message specific
behavior (notify, check access, various business methods) not relevant for
composer.
Specifications
* remove inherit from mail.message;
* re-define used fields;
* ensure everything still works;
Commit linked to task ID 1907153 and PR #28464
Signed-off-by: Xavier Dollé (xdo) <xdo@odoo.com>
Thibault Delavallée
8160c62a5b