[Bug]: Can rename category group to duplicate another group

[carkom]

Verified issue does not already exist?

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What happened?

PR #2262 blocked creating new category groups with duplicate names but it left out renaming existing category groups to already used names. If you create a new group, call it "test", then rename it to an existing category group name it will allow you to duplicate the group name. This should be blocked just like creating new ones.

[FlorianLang06]

I would like fix this bug. It's my first issue I try to solve. But I hope I can fix this.