[8.0] IAM2CS: ForceNickname, fix duplicate accounts for users

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/10902080612

Failed:

integration cherry-pick 3fc58a8e9 into integration failed check merge conflicts on a local copy of this repository

git fetch upstream
git checkout upstream/integration -b cherry-pick-2-3fc58a8e9-integration
git cherry-pick -x -m 1 3fc58a8e9
# Fix the conflicts
git cherry-pick --continue
git commit --amend -m 'sweep: #7784 IAM2CS: ForceNickname, fix duplicate accounts for users' --author='Andre Sailer <andre.philippe.sailer@cern.ch>'
git push -u origin cherry-pick-2-3fc58a8e9-integration

# If you have the GitHub CLI installed the PR can be made with
gh pr create \
   --label 'sweep:from rel-v8r0' \
   --base integration \
   --repo DIRACGrid/DIRAC \
   --title '[sweep:integration] IAM2CS: ForceNickname, fix duplicate accounts for users' \
   --body 'Sweep #7784 `IAM2CS: ForceNickname, fix duplicate accounts for users` to `integration`.

Adding original author @andresailer as watcher.

BEGINRELEASENOTES

*ConfigurationSystem
CHANGE: VOMS2CSAgent: if a nickname is set, this nickname will always be used and no new accounts are going to be created if a DN changes or a user is in multiple VOs
NEW: VOMS2CSAgent: New option "ForceNickname", if this option is enabled no dirac user is created if no nickname attribute is set for a user
CHANGE: IAMService: use logger and return errors for users so that the VOMS2CSAgent can notify admins about issues

ENDRELEASENOTES
Closes #7795'

DIRACGrid / DIRAC

[8.0] IAM2CS: ForceNickname, fix duplicate accounts for users #7784

Failed: