Send invites only if invited during the sync request

Fixes: https://git.koesters.xyz/timo/conduit/issues/175

src/client_server/sync.rs

@@ -391,6 +391,31 @@ pub async fn sync_events_route(
     let mut invited_rooms = BTreeMap::new();
     for room_id in db.rooms.rooms_invited(&sender_id) {
         let room_id = room_id?;
+        let mut invited_since_last_sync = false;
+        for pdu in db
+            .rooms
+            .pdus_since(&sender_id, &room_id, since)?
+            .filter_map(|r| r.ok())
+        {
+            if pdu.kind == EventType::RoomMember {
+                if pdu.state_key == Some(sender_id.to_string()) {
+                    let content = serde_json::from_value::<
+                        Raw<ruma::events::room::member::MemberEventContent>,
+                    >(pdu.content.clone())
+                    .expect("Raw::from_value always works")
+                    .deserialize()
+                    .map_err(|_| Error::bad_database("Invalid PDU in database."))?;
+                    if content.membership == ruma::events::room::member::MembershipState::Invite {
+                        invited_since_last_sync = true;
+                        break;
+                    }
+                }
+            }
+        }
+
+        if !invited_since_last_sync {
+            continue;
+        }
 
         let invited_room = sync_events::InvitedRoom {
             invite_state: sync_events::InviteState {