PURPOSE
Mass mailing is currently a bit messy. As SMS will be added as a way to notify
people in mass through SMS let us take this opportunity to somehow clean this
application: organization, light code cleaning, model renaming.
SPECIFICATIONS
Rename mail.mass_mailing model to mailing.mailing. Rationale :
* mailing is now a prefix for mass mailing models;
* mailing.mailing is easier to read / find / understand;
Note that mail.mass_mailing.campaign is not updated as it is likely to be
removed soon and replaced by simple utm.campaign model.
MIGRATION
mail.mass_mailing model -> mailing.mailing
mail_mass_mailing table -> mailing_mailing
LINKS
Task ID 2037906
Preparing task ID 1997464 (SMS addition in mass mailing)
PR #34938
Thibault Delavallée
49d2899fbd