[FIX] resource_booking: autosubscribe resource partners

When some partner is a resource assigned to a booking, he should get auto-subscribed.

Inspired in OCA#42, but I'm changing that behavior.

@Tecnativa TT32148

resource_booking/models/resource_booking.py

@@ -532,6 +532,31 @@ def name_get(self):
             new.append((id_, name))
         return new
 
+    def _message_auto_subscribe_followers(self, updated_values, default_subtype_ids):
+        """Auto-subscribe and notify resource partners."""
+        result = super()._message_auto_subscribe_followers(
+            updated_values, default_subtype_ids
+        )
+        combination = (
+            self.env["resource.booking.combination"]
+            .sudo()
+            .browse(updated_values.get("combination_id"))
+        )
+        resource_partners = combination.mapped(
+            "resource_ids.user_id.partner_id"
+        ).filtered("active")
+        for partner in resource_partners:
+            result.append(
+                (
+                    partner.id,
+                    default_subtype_ids,
+                    "mail.message_user_assigned"
+                    if partner != self.env.user.partner_id
+                    else False,
+                )
+            )
+        return result
+
     def _message_get_suggested_recipients(self):
         """Suggest related partners."""
         recipients = super()._message_get_suggested_recipients()
@@ -541,12 +566,6 @@ def _message_get_suggested_recipients(self):
                 partner=record.partner_id,
                 reason=self._fields["partner_id"].string,
             )
-            for partner in record.combination_id.resource_ids.user_id.partner_id:
-                record._message_add_suggested_recipient(
-                    recipients,
-                    partner=partner,
-                    reason=self._fields["combination_id"].string,
-                )
         return recipients
 
     def action_schedule(self):

resource_booking/tests/test_backend.py

@@ -589,7 +589,7 @@ def test_attendee_not_autoassigned_autoconfirmed(self):
         # Combination was handpicked, so resource attendees are auto-confirmed
         self.assertEqual(resource_attendees.state, "accepted")
 
-    def test_suggested_recipients(self):
+    def test_suggested_and_subscribed_recipients(self):
         # Create a booking as a new user
         rb_user = new_test_user(
             self.env, login="rbu", groups="base.group_user,resource_booking.group_user"
@@ -607,21 +607,12 @@ def test_suggested_recipients(self):
                 }
             )
         )
-        # Organizer and creator must already be following
+        # Organizer, combination and creator must already be following
         self.assertEqual(
-            rb.message_partner_ids, rb_user.partner_id | self.users[1].partner_id
+            rb.message_partner_ids, rb_user.partner_id | self.users[:2].partner_id
         )
         # Requester and combination must be suggested
         self.assertEqual(
             rb._message_get_suggested_recipients(),
-            {
-                rb.id: [
-                    (rb.partner_id.id, "some customer", "Requester"),
-                    (
-                        self.users[0].partner_id.id,
-                        "User 0<user_0@example.com>",
-                        "Resources combination",
-                    ),
-                ]
-            },
+            {rb.id: [(rb.partner_id.id, "some customer", "Requester")]},
         )