Function register_with 

pub fn register_with(
    lua: &Lua,
    conn: Arc<Mutex<Connection>>,
    interrupt: Arc<InterruptHandle>,
    cfg: SqlConfig,
) -> LuaResult<()>

Register std.kv with caller-provided SqlConfig.

If std.sql was registered earlier with a SqlConfig, the same slot in lua.app_data is overwritten — pass an identical config from the host to keep sql and kv in sync (the typical case).