support timestamped appservice messaging

Co-authored-by: strawberry <strawberry@puppygock.gay>
Signed-off-by: strawberry <strawberry@puppygock.gay>

src/api/server/make_join.rs

@@ -139,6 +139,7 @@ pub(crate) async fn create_join_event_template_route(
 			unsigned: None,
 			state_key: Some(body.user_id.to_string()),
 			redacts: None,
+			timestamp: None,
 		},
 		&body.user_id,
 		&body.room_id,