curl --request POST \
  --url https://cloud.kaneo.app/api/task-relation \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "sourceTaskId": "<string>",
  "targetTaskId": "<string>",
  "relationType": "subtask"
}
'

{
  "id": "<string>",
  "sourceTaskId": "<string>",
  "targetTaskId": "<string>",
  "relationType": "<string>",
  "createdAt": "2023-11-07T05:31:56Z"
}