Be able to activate/block the "automatic closing message" for a particular chat.

This request is coming from our Spanish Client Euroinnova. They need the option for the agent, while in the chat, to close the conversation but decide whether or not to activate the closing message for that particular chat. That is, the closing message would be active by default for all chats (as it currently works), but they need the agent to be able to decide to deactivate the message for a particular conversation after closing it so that the closing message is not sent.