List heartbeats

curl --request GET \
  --url https://api.rootly.com/v1/heartbeats \
  --header 'Authorization: Bearer <token>'

{
  "data": [
    {
      "id": "<string>",
      "type": "heartbeats",
      "attributes": {
        "name": "<string>",
        "description": "<string>",
        "alert_summary": "<string>",
        "alert_urgency_id": "<string>",
        "interval": 123,
        "interval_unit": "seconds",
        "notification_target_id": "<string>",
        "notification_target_type": "User",
        "enabled": true,
        "status": "waiting",
        "ping_url": "<string>",
        "secret": "<string>",
        "last_pinged_at": "<string>",
        "expires_at": "<string>",
        "created_at": "<string>",
        "updated_at": "<string>"
      }
    }
  ],
  "links": {
    "self": "<string>",
    "first": "<string>",
    "prev": "<string>",
    "next": "<string>",
    "last": "<string>"
  }
}