Function read_provider_original 

async fn read_provider_original(
    provider: &Arc<Provider>,
    key: &str,
) -> Result<Option<Bytes>>

Reads one original from the source storage provider. An absent object is skipped (Ok(None)) like a dangling filesystem row; a transient fault is retried up to PROVIDER_READ_ATTEMPTS times, and a persistent one aborts the import with an Err.