Function receive_and_finalize_object 

fn receive_and_finalize_object<ObjectID: FsVerityHashValue>(
    rx: Receiver<Bytes>,
    size: u64,
    repo: &Repository<ObjectID>,
) -> Result<ObjectID>

Receive data from channel, write to tmpfile, compute verity, and store object.

This runs in a blocking task to avoid blocking the async runtime.