[FIX] mass_mailing: no multi language edit

Creating and editing mass mailing in multiple language is managed with
the change 05daa152.

But currently the language the mass mailing is sent in, is the language
of the "Process Mass Mailing Queue" (root user if not changed) so all
the recipients will receive the mail in the root user language has at
the time the given batch of mails is sended.

So this is different from what someone could expect by it being
translatable. In any case the recipients list could be based on a lead,
a partner a mass mailing contact or other and a language could not be
determinable in stable (a mass mailing contact does not have a language
for example).

If the system worked, there is also a usability downside in the meaning
that someone could duplicate a mail and not check all translation and
not be aware that the mail he see is maybe not the mail that will be
received (if translations have not all been completed).

In stable to have the same behavior in any case and lessen the usability
burden of users thinking erroneously the mass mailing may be sent in
several languages depending on a not-existing heuristic, this changeset
remove the translatability of mass mailing content.

This has the following effect:

no translation editing appear,
the mass mailing is edited and sent in one and the same language,
If someone want to send a mass mailing in several language, currently in
Odoo it would then require to:

duplicate the mass mailing,
change the domains of recipients base on choosen heuristic,
edit the duplicated mass mailing in the choosen language

opw-746445
opw-746776
closes #17718

addons/mass_mailing/models/mass_mailing.py

@@ -487,7 +487,7 @@ class MassMailing(osv.Model):
         'create_date': fields.datetime('Creation Date'),
         'sent_date': fields.datetime('Sent Date', oldname='date', copy=False),
         'schedule_date': fields.datetime('Schedule in the Future'),
-        'body_html': fields.html('Body', translate=True),
+        'body_html': fields.html('Body'),
         'attachment_ids': fields.many2many(
             'ir.attachment', 'mass_mailing_ir_attachments_rel',
             'mass_mailing_id', 'attachment_id', 'Attachments'

addons/web_editor/static/src/js/backend.js

@@ -183,6 +183,11 @@ var FieldTextHtml = widget.extend({
     template: 'web_editor.FieldTextHtml',
     willStart: function () {
         var self = this;
+
+        if (this.field.translate === false) {
+            this.languages = [];
+            return $.when();
+        }
         return new Model('res.lang').call("search_read", [[['code', '!=', 'en_US']], ["name", "code"]]).then(function (res) {
             self.languages = res;
         });