use Debug;
/// Per-call backend extras for [`UniversalReadFs::open`].
///
/// Marker trait for the value passed to
/// [`UniversalReadFs::open`](super::UniversalReadFs::open) as `extra`.
/// Implementers expose typed setters so generic-over-`Fs` callers can opt
/// into backend-specific knobs without naming the concrete extras type.
///
/// `Default` is required so callers can construct a neutral extras value
/// (e.g. `<Fs::OpenExtra>::default()`) and then chain typed setters.