No way to set content type of each param in multipart

[darkmakukudo]

Request Method: POST
Referrer Policy: no-referrer-when-downgrade
Cache-Control: no-cache, no-store, must-revalidate
Connection: keep-alive
Content-Length: 579
Content-Type: application/json
Date: Mon, 02 Apr 2018 09:47:17 GMT
Server: Apigee Router
Accept: application/json
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Connection: keep-alive
Content-Length: 478592
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryV2XWWBaHohtZIDEg
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36
X-Requested-With: XMLHttpRequest
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="guid"

9ffffba4-2f14-4e93-9c59-c03e67262b47
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="json"
// Ability to set the content type for each part

{"name":"test.png"}
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="qquuid"

d07f56d9-5b41-49f9-8fd1-d1ea29be4a16
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="qqfilename"

test.png
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="qqtotalfilesize"

477560
------WebKitFormBoundaryV2XWWBaHohtZIDEg
Content-Disposition: form-data; name="file"; filename="test.png"
Content-Type: image/png

------WebKitFormBoundaryV2XWWBaHohtZIDEg--