curl --request DELETE \
  --url https://{cluster}.voucherify.io/v1/rewards/{rewardId} \
  --header 'Authorization: Bearer <token>' \
  --header 'X-App-Id: <api-key>' \
  --header 'X-App-Token: <api-key>'

{
  "code": 400,
  "key": "resource_in_use",
  "message": "Resource in use",
  "details": "Resource reward with id rew_fcYALROsORec6cP0VBItCVfq is in use by reward_assignments with ids [rewa_5WV7H3y2lT3GGl03Xjw29IEc]",
  "request_id": "v-0b8c7b967950216291",
  "related_object_ids": [
    "rewa_5WV7H3y2lT3GGl03Xjw29IEc"
  ],
  "related_object_type": "reward_assignment"
}