struct Message<T> {
    kind: String,
    payload: T,
}
trait MessageHandler<T> {
    fn can_handle_message_kinds(&self) -> [String];
    fn handle(&self, msg: &Message<T>);
}
trait Mediator {
    fn register<T>(handler: dyn MessageHandler<T>);
    fn signal<T>(msg: &Message<T>);
}

mod mediator;