List subscription tiers

{
  "tiers": [
    {
      "credit_allocation_usd": 0.1,
      "credit_rollover_months": 0,
      "display_name": "string",
      "max_concurrent_jobs": 0,
      "max_pages_per_crawl": 0,
      "monthly_extractions": 0,
      "name": "string",
      "requests_per_minute": 0
    }
  ]
}

{
  "detail": "Property foo is required but is missing.",
  "errors": [
    {
      "location": "string",
      "message": "string",
      "value": null
    }
  ],
  "instance": "https://example.com/error-log/abc123",
  "status": 400,
  "title": "Bad Request",
  "type": "https://example.com/errors/example"
}