curl --request GET \
  --url https://api.eu.bronto.io/groups/{groupId}/members \
  --header 'X-BRONTO-API-KEY: <api-key>'

{
  "members": [
    {
      "group_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "member_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "member_type": "USER",
      "modified_at": 123
    }
  ]
}