List alert sources

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

{
  "data": [
    {
      "id": "<string>",
      "type": "alert_sources",
      "attributes": {
        "alert_urgency_id": "<string>",
        "name": "<string>",
        "source_type": "<string>",
        "status": "<string>",
        "secret": "<string>",
        "webhook_endpoint": "<string>",
        "created_at": "<string>",
        "updated_at": "<string>",
        "sourceable_attributes": {}
      }
    }
  ],
  "links": {
    "self": "<string>",
    "first": "<string>",
    "prev": "<string>",
    "next": "<string>",
    "last": "<string>"
  }
}