Hadolint Dockerfile improvement suggestions.

Hi there,

does it make sense, if I make PRs to fix Hadollint issues within the Dockerfiles?
I made a PR to implement Hadolint in the past, but it never got merged. If you ack this, I would start working on this and make PRs.
https://github.com/DefectDojo/django-DefectDojo/pull/9839/files

Best Regards