--{boundary}
Content-Disposition: form-data; name="post"; filename="post.json"
Content-Type: application/vnd.tent.post.v0+json; type="https://custom.type/v0#"
Content-Length: 47

{"type":"https://custom.type/v0#","content":{}}
--{boundary}
Content-Disposition: form-data; name="text[0]"; filename="text.txt"
Content-Type: text/plain
Content-Length: 24

Some Text
And a bit more
--{boundary}--