add typedef for pdu_ids

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/rooms/timeline/pduid.rs

@@ -0,0 +1,13 @@
+use crate::rooms::short::{ShortEventId, ShortRoomId};
+
+#[derive(Clone, Copy)]
+pub struct PduId {
+	_room_id: ShortRoomId,
+	_event_id: ShortEventId,
+}
+
+pub type RawPduId = [u8; PduId::LEN];
+
+impl PduId {
+	pub const LEN: usize = size_of::<ShortRoomId>() + size_of::<ShortEventId>();
+}