public FMUCHandler getFmucHandler() {
        return fmucHandler;
    }
Sends the rejection to the inviter. The rejection will be sent as if the room is rejecting
the invitation is named of the invitee. The rejection will include the address of the invitee
together with the reason for the rejection if any. Since the inviter could be offline at the
moment we need the originating session so that the offline strategy could potentially bounce
the message with the rejection.

@param to the JID of the user that is originated the invitation.
@param reason the reason for the rejection or null if none.
@param sender the JID of the invitee that is rejecting the invitation.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/MUCRoom.java