Is the DataVolumeCategory really needed ?

[eric-murray]

Problem description

• is the DataVolumeCategory really needed ? Using an ENUM seems to limit the usability of the API, as well as being a bit arbitrary), while just a unit and an integer value (as done in volumeToCheck) could be enough and more flexible, so just a schema called "DataVolume" could serve both purposes. For the unit, also the above "MiB/GiB" question applies (as opposed to more usual "MB"/"GB" units)