[FIX] test_mail: test for conflicting partner_id on subscribe

From opw-2200219 opw-2210285 (v12)

Use case (2200219):
- Install CRM, sales and Automated Action
- Create the automated action
  * Model -> Sale Order
  * Trigger Condition -> On creation
  * Action To Do -> Add followers
  * Add Channels -> sales
- Create a new CRM opportunity with a partner set, Save
- Click on the "New quotation"
- Save

A Traceback "Error: A follower must be either a partner or
a channel (but not both)." will popup, blocking the user from
completing the action.

Use case (2210285):
After adding a channel as a follower to a sales team it is not
possible to create a sale order from a contact or opportunity. You can
only create a sale order from the sales app in that case.

End of use cases-----

This occur because the context flag default_partner_id is used by
the model to override the empty partner_id which should remain empty

Fixed in v12, forwarding the test for v13 and upward

closes odoo/odoo#48476

X-original-commit: 049aa5c2297938bcd378d1dee1aa766a646cb461
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/test_mail/tests/test_mail_followers.py

@@ -117,6 +117,16 @@ class BaseFollowersTest(TestMailCommon):
                 'channel_id': self.channel_listen.id,
             })
 
+    def test_followers_default_partner_context(self):
+        """Test that a follower partner_id is not taken from context
+           when channel id is also defined.
+        """
+        test_record = self.test_record.with_user(self.user_employee)
+        test_record.with_context(default_partner_id=1).message_subscribe(
+            partner_ids=[self.user_employee.partner_id.id, self.user_admin.partner_id.id],
+            channel_ids=[self.channel_listen.id]
+        )
+
 
 class AdvancedFollowersTest(TestMailCommon):
     @classmethod