List Group Managers

curl --request GET \
  --url https://api.example.com/groups/{group_id}/managers

{
  "managers": [
    {
      "group_id": "<string>",
      "id": "<string>",
      "member_id": "<string>",
      "created_at": "2023-11-07T05:31:56Z"
    }
  ]
}