QUARANTINE <nick> :<reason>

Applies user mode +q to nick, preventing them from
taking the following actions:

- Joining channels (except channels allowed in
  quarantine::allow_channels)
- Sending messages to channels (except channels
  allowed in quarantine::allow_channels)
- Sending messages to users (except services and
  opers)

Users who are not opers or marked as services will
additionally be unable to send private messages to
quarantined users.

A quarantined user who identifies to services will
automatically lose the +q user mode. Attempting to
use this command on a user already identified to
services will fail.

- Requires oper priv: oper:quarantine
