Promote Label to Group Label via API endpoint

I want to promote a project label to a group label via the API.

You can promote a project label to a group label in the interface, like so:

But you can't do the same via the API. It'd be nice if you could :)

Related: #53861 (closed), !21368 (merged)

See also https://docs.gitlab.com/ce/api/group_labels.html and https://docs.gitlab.com/ce/api/labels.html