This patch is not backward compatible with its original,
but it's considered fine, since the original workload types were not
yet part of any release.
The changes include:
- instead of using 'unspecified' for declaring that there's no workload
type for a particular service level, NULL is used for that purpose;
NULL is the standard way of representing lack of data
- introducing a delete marker, which accompanies NULL and makes it
possible to distinguish between wanting to forcibly reset a workload
type to unspecified and not wanting to change the previous value
- updating the tests accordingly
These changes come in as a single patch, because they're intertwined
with each other and the tests for workload types are already in place;
an attempt to split them proved to be more complicated than it's worth.
Tests: unit(release)
Closes#8763
389a0a52c9