1. simplify message reaction formatter (personas)
Data was formatted to have "partners" and "guests" entries, both
of which contribute to personas.
To avoid some post-processing of data in JS, it's best to format
data to immediately include type of persona.
2. include "guestAuthor" in "author" data of message
Discuss models in JS group partners and guests into a single model
Persona, to make feature works regardless on whether user is
authenticated or not.
This commit simplifies code by removing data guestAuthor in message
formatted data, and instead author contains author data in all cases,
whether the author is a partner or guest.
3. simplify insert (remove id, redundant with preinsert)
Also rename Follower.isActive to Follower.is_active, for
even simpler Follower.insert()
closesodoo/odoo#137276
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>