Function room_join_request_event 

pub fn room_join_request_event(
    actor: AgentId,
    created_at: i64,
    nonce: u64,
    room_id: impl Into<String>,
    payload: RoomJoinRequestPayload,
) -> Event<RoomJoinRequestPayload>

A room.join.request carries room_id but no base: its author may not be able to read the room.