add stub for database benches

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

src/database/benches.rs

@@ -0,0 +1,17 @@
+#[cfg(conduwuit_bench)]
+extern crate test;
+
+#[cfg(conduwuit_bench)]
+#[cfg_attr(conduwuit_bench, bench)]
+fn ser_str(b: &mut test::Bencher) {
+	use conduwuit::ruma::{RoomId, UserId};
+
+	use crate::ser::serialize_to_vec;
+
+	let user_id: &UserId = "@user:example.com".try_into().unwrap();
+	let room_id: &RoomId = "!room:example.com".try_into().unwrap();
+	b.iter(|| {
+		let key = (user_id, room_id);
+		let _s = serialize_to_vec(key).expect("failed to serialize user_id");
+	});
+}