Get app metered usage

curl --request GET \
  --url https://cloud-api.phala.com/api/v1/apps/{app_id}/usage

{
  "usage": [
    {
      "instance_id": "<string>",
      "project_id": 123,
      "team_id": 123,
      "timestamp": "<string>",
      "event_type": "<string>",
      "cost": 123,
      "details": "<string>",
      "usage_type": "<string>",
      "billing_start": "<string>",
      "billing_end": "<string>",
      "duration_minutes": 123,
      "billing_key": "<string>",
      "billing_hour": "<string>",
      "billing_day": "<string>"
    }
  ],
  "total": 123,
  "total_cost": 123
}