Sync once on bot startup

src/bot.rs

@@ -297,6 +297,8 @@ impl Bot {
     /// Runs the bot. This function does not return except in case of error.
     #[instrument(skip(self))]
     pub async fn run(mut self) -> Result<Never> {
+        self.client.sync_once(SyncSettings::default()).await?;
+
         self.join_announce_rooms()
             .await
             .wrap_err("failed to join announcement rooms")?;