chore: make PreparationUtils static again.

[fhuaulme]

Link to the JIRA issue (no jira)

Please check if the PR fulfills these requirements

• [x] The commit(s) message(s) follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)
• [ ] The code coverage on new code is > 75 % for backend and > 95% for frontend
• [ ] The new code does not introduce new technical issues (sonar / eslint)
• [ ] Functional tests have been performed
• [ ] Docker configuration files for config-std or config-cloud profiles are impacted

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• [ ] No, that's bad, this PR should not be merged !
• [x] No, and no need to (backend changes only)