[8.0][mass_mailing][FIX] rename mailing_type into mailing model
[8.0][mass_mailing][FIX] allow to reply into document that inherit from 'mail.thread'
[8.0][mass_mailing][FIX] add missing fields when creating a new 'mail.mass_mailing' from 'mail.compose.message'
[8.0][mass_mailing][FIX] repair sql request