[IMP] mail: update _notify API

Purpose of this commit is to allow to give additional values when rendering
notification emails and to make some parameters explicit.

This commit updates the _notify API. It allow to propagate a dictionary
containing values given to the rendering of the notification template.
This allow to have more complex templates and/or to control the rendering
depending on some parameters. Indeed currently only some fixed values and
values coming form the message to notify are given to the rendering
context.

First use will be soon when pushing notification emails not necessarily
linked to documents. In this process some values will be given by the caller
and not only by the message context anymore.

This commit also moves some context key used to control the notification
process directly in values given to the _notify method. It allows to make
those parameters explicit and rely less on context.

The _notify method now takes a values dictionary that may contain

 * add_sign: add user signature to notification email, default is True.
   It replaces the ``mail_notify_user_signature`` context key;
 * mail_auto_delete: auto delete send emails, default is True. It
   replaces the ``mail_auto_delete`` context key;
 * other values are given to the context used to render the notification
   template, allowing customization.

It allows to remove some context switch notably in the composer. A values
dictionary is computed and given to message_post and then propagated to
the notification mechanism.

1 files changed, 3 insertions, 2 deletions

diff --git a/addons/test_mail/tests/test_message_compose.py b/addons/test_mail/tests/test_message_compose.py
index e2668cdac45..6fe72d4da6f 100644
--- a/addons/test_mail/tests/test_message_compose.py
+++ b/addons/test_mail/tests/test_message_compose.py
@@ -63,10 +63,11 @@ class TestMessagePost(BaseFunctionalTest, MockEmails, TestRecipients):
     def test_post_notifications_keep_emails(self):
         self.test_record.message_subscribe_users(user_ids=[self.user_admin.id])
 
-        msg = self.test_record.sudo(self.user_employee).with_context(mail_auto_delete=False).message_post(
+        msg = self.test_record.sudo(self.user_employee).message_post(
             body='Test', subject='Test',
             message_type='comment', subtype='mt_comment',
-            partner_ids=[self.partner_1.id, self.partner_2.id]
+            partner_ids=[self.partner_1.id, self.partner_2.id],
+            notif_values={'mail_auto_delete': False}
         )
 
         # notifications emails should not have been deleted: one for customers, one for user