User Contribution Mapping - Placeholder users can be added as regular members via the API

As reported in the test session issue, placeholders can be added as members of the group (not as placeholders) by doing a simple API call:

curl 'https://import-metrics-3k.1fd5a570.gcp.gitlabsandbox.net/api/v4/groups/52819/invitations' -X POST -H "PRIVATE-TOKEN: glpat-..." -d 'user_id=39308&access_level=50'

{"status":"success"}%