Get EndUser named dates

curl --request GET \
  --url https://app.herondata.io/api/end_users/{end_user_id_or_heron_id}/named_dates \
  --header 'Authorization: Basic <encoded-value>'

{
  "named_dates": [
    {
      "date": "2025-03-04",
      "name": "last_transaction"
    }
  ]
}