Revert "Re #6577 Move dgs_utils.py to API v2"

I'm reverting this commit because (a) it really has nothing to do with the rest of this ticket &
(b) the changes don't work.
This file will instead be migrated under dedicated ticket #7547.
This reverts commit 08cd5a97d56beb0ab4aaa9f86225c8e4eff7d697.
Merge branch 'feature/6577_reduction_gui' into develop