`POST /groups` doesn't work on gitlab.com

Background

In !139842 (merged) we added an organization_id attribute to POST /groups so we can create a group in an organization. We are using this API on https://gitlab.com/-/organizations/default/groups/new. What we didn't realize is POST /groups does not allow creating top level groups on gitlab.com. Related code is in https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/ee/api/groups.rb#L72.

Solutions

• Is there a way we can allow use of this API for this context?
• Do we need to consider an alternative API or making a request to a Rails controller?