Add guidelines for hiding the UI on empty states
@dmoraBerlin and I have been chatting on Slack about the work we're doing on the empty group page: gitlab-org/gitlab#267014 (closed) This issue has been open for a while and now we've aligned on showing the main two options that make most sense in an empty group and hiding the UI that is usually on a group page. Daniel then warned me about Taurie's comment on another issue that could be related: gitlab-org/gitlab!78012 (comment 923457878)
Proposal
Let's add some guidance to the empty state guidelines, establish that it's ok to hide the UI in some occasions but that it needs to be carefully thought through as there are cases when showing the UI, even if there's seemingly nothing to show still makes sense and offers more value to the user and hence produces a better user experience.