Automatically clear external media that were added from a playlist
Currently if we ingest a playlist containing an external media, then update the playlist to remove that media, we will have a stalled media & file in the database.
We can't remove it directly when refreshing the playlist though, otherwise we would lose the associated meta, which we want to keep if the media is still part of the playlist.
Maybe keeping them until they are considered outdated is enough, but this needs to be reviewed/verified.