Function until_finished 

async fn until_finished<F>(
    services: &Services,
    marker: &'static str,
    pass: F,
) -> Result
where
    F: AsyncFnOnce(&Services) -> Result<bool>,

Runs a pass whose work may wait on a condition outside the database.

The marker is stamped only once the pass reports it finished, so a pass that waits runs again on a later boot.