[bug#45692] [PATCH v5 3/3] gnu: Add ZFS service type.

[raid5atemyhomework]

**BUMP**

Come on, last patch, please?

If you are worried about not knowing anything about ZFS, please see this, which 
I used as reference: https://github.com/openzfs/zfs/discussions/11453

Otherwise, really, all I need to get reviewed is if the code is Guix-y enough 
to merge in.
I believe all the Scheme style guidelines are followed correctly at this point.

Thanks
raid5atemyhomework