servicemanager is a requirement
Merge branch 'hotfix/4157'

Close #4157
Merge pull request #4161 from gabriel403/patch-5

servicemanager is a requirement
[#4161] Mark ServiceManager as optional

- It's an optional dependency only, as the helper system is opt-in, via the
  renderers -- which are optional as well.
Merge branch 'hotfix/4161' into develop

Forward port #4161