pick the newest character for a slot when recreating

src/entity/gateway/postgres/migrations/V0010__char_create_timestamp.sql

@@ -0,0 +1,2 @@
+alter table player_character
+  add created_at timestamptz default current_timestamp not null;

src/entity/gateway/postgres/postgres.rs

@@ -276,17 +276,17 @@ async fn create_character(conn: &mut sqlx::PgConnection, char: NewCharacterEntit
 
 async fn get_characters_by_user(conn: &mut sqlx::PgConnection, user: &UserAccountEntity) -> Result<[Option<CharacterEntity>; 4], GatewayError>
 {
-    let mut stream = sqlx::query_as::<_, PgCharacter>("select * from player_character where user_account = $1 and slot < 4 order by slot")
+    let stream = sqlx::query_as::<_, PgCharacter>("select * from player_character where user_account = $1 and slot < 4 order by created_at;")
         .bind(user.id.0)
         .fetch(conn);
-    const NONE: Option<CharacterEntity> = None;
-    let mut result = [NONE; 4];
-    while let Some(character) = stream.try_next().await? {
-        let index = character.slot as usize;
-        result[index] = Some(character.into())
-    }
 
-    Ok(result)
+    Ok(stream.fold(core::array::from_fn(|_| None), |mut acc, char| {
+        if let Ok(char) = char {
+            let slot = char.slot as usize;
+            acc[slot] = Some(char.into())
+        }
+        acc
+    }).await)
 }
 
 async fn save_character(conn: &mut sqlx::PgConnection, char: &CharacterEntity) -> Result<(), GatewayError>