Saving Talk chats for audit purposes

#1 states that “chat logs are stored securely on your own server.” but I’ve not been able to locate them. Are they stored in a file or in the Nextcloud database?

Since a chat (conversation) can be deleted I’m assuming that the “chat logs” are removed. Is there a setting to preserve chat logs and just remove them from the UI? Is it possible to save Talk chats to a log file for audit purposes?