drop all previous indexes in migration

reason: most of it doesn't need real type,
but will simplificate alot without real ones

src/db/mod.rs

@@ -122,6 +122,12 @@ impl DB {
     }
 
     pub async fn migrate(&mut self) -> DbResult<()> {
+        let db = self.get_database().await;
+        /// some migrations doesn't realy need type of collection
+        type AnyCollection = Event;
+        db.collection::<AnyCollection>("events")
+            .drop_indexes()
+            .await?;
         let events = self.get_database().await.collection::<Event>("events");
         events
             .create_index(
@@ -132,12 +138,15 @@ impl DB {
             )
             .await?;
 
+        db.collection::<AnyCollection>("events")
+            .drop_indexes()
+            .await?;
         // clear callbacks after a day because otherwise database will contain so much data
         // for just button clicks
         let callback_info = self
             .get_database()
             .await
-            .collection::<Event>("callback_info");
+            .collection::<AnyCollection>("callback_info");
         callback_info
             .create_index(
                 IndexModel::builder()