"date_last_updated" isn't updated when a new issue is added to a volume

The value of "date_last_updated" doesn't get updated when issues are added to the volume. Because of that, there is no reliable way to determine if _anything_ changed about the volume metadata (description changed, issue added, issue description changed, etc.), leading to my application needing to make ATLEAST twice as much requests to the api, because for each volume, I'm required to also fetch ALL it's issues to make sure that the local metadata is up-to-date. There needs to be a value that the dev can use to determine if it's local metadata is in sync with the CV metadata, because then if not, it can fetch _only_ that volume to update it.