"Seal-off" channels

I have a server used to plan various events. Each event gets a channel for discussion and details of it.

However once the event has happened, I want to keep the channel for archival purposes, but I don't want anyone else typing in that channel, not even me and the other admins. So I think it would be very helpful if I could select a button in the channel settings called "seal channel". This would prevent any more messages being sent in that channel, or any messages being edited, unless the channel was unsealed

Sealing or unsealing a channel should be required to done by a server admin, and should require them to enter their password to confirm.