[ADD] mass_mailing: add a snippet to allow subscribing to a contact list (newsletter)
[IMP] website_mail, mass_mailing: icon in editor for the snippets + renaming
[MERGE] Sync with upstream (saas-4)
[FIX] Event - Allow to specify the timezone from the event and use it in template mail.
[FIX] Event - Don't update the context but a copy when we recompute dates with the timezone specified for the event.
[MERGE] Sync with upstream (saas-4)
[IMP] website_mail: rename newsletter mail group to discussion group
to avoid confusion with mass mailing mailing lists and newsletters.
[IMP] mass_mailing: added newsletter as mailing list data + imported contact still demo data
[IMP] subscribe to group / newsletter widgets: wording cleaning
[FIX] website_forum: correct the 'Editor' goal definition, the field author_id on a mail_message is a m2o to res.partner and not res.users
[MERGE] [ADD] mass_mailing: add a snippet to allow subscribing to a contact list (newsletter). Also cleaned the wording of the snippet allowing to subscribe do a discussion group to avoid confusion.