curl --request GET \
  --url https://api.zerion.io/v1/tx-subscriptions/ \
  --header 'Authorization: Basic <encoded-value>'

{
  "data": [
    {
      "type": "transactions_subscription",
      "id": "52d994a173d755e99845e861d534a419",
      "attributes": {
        "callback_url": "https://webhook.site/fcd606d2-f5bd-4832-9874-ff07c980b5a3",
        "created_at": "2022-08-15T11:26:31+00:00",
        "updated_at": "2022-08-15T11:26:31+00:00"
      },
      "relationships": {
        "chains": [
          {
            "links": {
              "related": "https://api.zerion.io/v1/chains/polygon"
            },
            "data": {
              "type": "chains",
              "id": "polygon"
            }
          }
        ]
      }
    }
  ]
}