curl --request GET \
  --url https://app.sendmux.ai/api/v1/mailbox/usage \
  --header 'Authorization: Bearer <token>'

{
  "meta": {
    "request_id": "req_clxxxxxxxxxxxxxxxxxxxxxxxxx"
  },
  "data": {
    "resources": [
      {
        "quota_id": "<string>",
        "name": "<string>",
        "resource_type": "<string>",
        "scope": "<string>",
        "types": [
          "<string>"
        ],
        "used": 123,
        "hard_limit": 123,
        "warn_limit": 123,
        "soft_limit": 123,
        "percent_used": 123
      }
    ],
    "states": {
      "quota_state": "<string>"
    }
  }
}