entity.contributors: should adding the same actor in different roles be allowed?

when adding entity contributors, the backend currently checks that actor.id is unique. this prevents adding the same actor in different roles, e.g. as both "contributor" and "author". this might be intentional, just want to make sure that we don't want to use a compound constraint of actor.id+role.code here?

example:

curl -X POST -d '{"label":"Label","description":"","contributors":[{"role":{"code":"contributor"},"actor":{"id":1}},{"role":{"code":"author"},"actor":{"id":1}}]}' -H "Content-Type: application/json" -H "Authorization: ..." "http://localhost:8080/api/datasets" | jq