POST with form-data body is missing a boundary

[chis-j]

When sending a POST request with a form-data body, the Content-Type header just contains "multipart/form-data" and thus is missing a boundary.
This results into no form data to be found by the server.

Expected result:
A request with a Content-Type like: "multipart/form-data; boundary=--------------------------636776427956514692483101" is sent.