Function spawn_enqueue_with_callback 

pub(crate) fn spawn_enqueue_with_callback<F>(
    ctx: Arc<AppContext>,
    album: Option<(String, String)>,
    paths: Vec<PathBuf>,
    on_complete: F,
)
where
    F: FnOnce(usize, usize) + 'static,

Enqueue files for upload and invoke on_complete(queued, skipped) on the main context when all files have been hashed and enqueued.