Invalid group/subgroup names e.g. 'api/v4'
Summary
Users are able to create (sub)groups with names like "api/v4". Those groupnames are not valid due to a conflict with the API/URL.
Steps to reproduce
Create a group named "api". Create a subgroup named "api/v4".
What is the current bug behavior?
Gitlab does create a group called "api".
What is the expected correct behavior?
Gitlab should deny groups and usernames with the name "api" or whatever leads into a url like "https://gitlabserver/api".
Gitlab-Version
9.0.2