Fix joining descendant channels, style channel invites

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/collab/src/tests/channel_tests.rs

@@ -313,6 +313,38 @@ fn assert_members_eq(
     );
 }
 
+#[gpui::test]
+async fn test_joining_channel_ancestor_member(
+    deterministic: Arc<Deterministic>,
+    cx_a: &mut TestAppContext,
+    cx_b: &mut TestAppContext,
+) {
+    deterministic.forbid_parking();
+    let mut server = TestServer::start(&deterministic).await;
+
+    let client_a = server.create_client(cx_a, "user_a").await;
+    let client_b = server.create_client(cx_b, "user_b").await;
+
+    let parent_id = server
+        .make_channel("parent", (&client_a, cx_a), &mut [(&client_b, cx_b)])
+        .await;
+
+    let sub_id = client_a
+        .channel_store()
+        .update(cx_a, |channel_store, _| {
+            channel_store.create_channel("sub_channel", Some(parent_id))
+        })
+        .await
+        .unwrap();
+
+    let active_call_b = cx_b.read(ActiveCall::global);
+
+    assert!(active_call_b
+        .update(cx_b, |active_call, cx| active_call.join_channel(sub_id, cx))
+        .await
+        .is_ok());
+}
+
 #[gpui::test]
 async fn test_channel_room(
     deterministic: Arc<Deterministic>,