output multipart/form-data
---
{
  "parts": {
    "first": {
      "headers": {
        "Content-Disposition": {
          "name": "first",
          "subtype": "form-data"
        }
      },
      "content": "I"
    },
    "second": {
      "headers": {
        "Content-Disposition": {
          "name": "second",
          "subtype": "form-data"
        }
      },
      "content": ""
    }
  }
}