[IMP] mail: add default explicitly in channel_create to be more clear

Specify 'channel_type' explicitly in channel_create. This makes the
method more clear and decoupling from default value.
Once the default values changes, the method can work as expected as well.

task-2767635

closes odoo/odoo#84867

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/models/mail_channel.py

@@ -1073,6 +1073,7 @@ class Channel(models.Model):
         """
         # create the channel
         new_channel = self.create({
+            'channel_type': 'channel',
             'name': name,
             'public': privacy,
         })