Part of [ENG-4319](https://linear.app/comm/issue/ENG-4319/warn-the-user-when-deleting-a-chat-that-has-contained-chats).
Before deletion, the user is warned about possible contained chats. For subchannel deletion, the modal looks like this:
{F642476}
When deleting a whole community, message changes:
{F642488}
When there are no contained chats, the confirmation modal does not pop up.
Depends on D8526.