    POST http://localhost:8000/form-params
    [FormParams]
    param1: value1
    param2:
    param3: a=b
    param4: a%3db
    values\u{5b}0\u{5d}: 0
    values[1]: 1

    HTTP/1.0 200

    # same version as raw
    POST http://localhost:8000/form-params
    Content-Type: application/x-www-form-urlencoded
    ```param1=value1&param2=&param3=a%3db&param4=a%253db&values[0]=0&values[1]=1```

    HTTP/1.0 200