Try to sync up to 4 times after joining a room

It seems like sometimes one sync isn't enough after sending the join
request.

src/matrix.rs

@@ -23,6 +23,7 @@ use matrix_sdk::{
     BaseRoom, Client,
 };
 use serde::de;
+use tokio::time::sleep;
 
 use crate::config::Config;
 
@@ -81,10 +82,14 @@ pub async fn ensure_room_joined(matrix_client: &Client, room_id: &OwnedRoomOrAli
             .iter()
             .find(|a_room| room_matches(a_room, room_id))
         {
+            info!("Accepting invitation to room {room_id}");
             invited.join().await?;
         } else {
+            info!("Joining room {room_id}");
             matrix_client.join_room_by_id_or_alias(room_id, &[]).await?;
         }
+
+        for _ in 0..4 {
             let settings = build_sync_settings().await;
             matrix_client.sync_once(settings).await?;
             room = matrix_client
@@ -92,6 +97,11 @@ pub async fn ensure_room_joined(matrix_client: &Client, room_id: &OwnedRoomOrAli
                 .iter()
                 .find(|a_room| room_matches(a_room, room_id))
                 .cloned();
+            if room.is_some() {
+                break;
+            }
+            sleep(Duration::from_millis(500)).await;
+        }
     }
 
     room.ok_or_else(|| anyhow!("Unable to join room {}", room_id))