update mockrooms so join emits join message

secert-hitler/src/model/state/room.rs

@@ -1,9 +1,11 @@
 use super::event;
 
 pub trait Room {
+   fn rollback(&mut self, since: String);
    fn sync(&mut self) -> Vec<event::Event>;
    fn send(&mut self, message: String) -> Result<&str, &str>;
    fn room_id(&self) -> String;
+   fn since(&self) -> String;
 }
 
 #[cfg(test)]