curl --request POST \
  --url https://api-{region}.sesametime.com/project/v1/planned-tasks-assignations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "plannedTaskId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "entityReference": {
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "type": "employee"
  }
}
'

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
}