PUT request without stringify'ing body returns 500

[BrennanAyers]

Steps to reproduce:

• Note the lack of stringifying the body object

fetch('https://jsonplaceholder.typicode.com/posts/1', {
    method: 'PUT',
    body: {
      id: 1,
      title: 'foo',
      body: 'bar',
      userId: 1
    },
    headers: {
      "Content-type": "application/json; charset=UTF-8"
    }
  })
  .then(response => response.json())
  .then(json => console.log(json))

Expected response:

400 Bad Request

Actual response:

500 Internal Server Error

---

I believe it has something to do with the mismatch in the Content-Type and the input. If the Content-Type header is set to application/x-www-form-urlencoded, the response will return a 200, but with the following body:

{
  "[object Object]": "",
  "id": 1
}