NiFi InvokeHttp: How to send multiple files with multipart/form-data without ExecuteGroovyScript

Normally, when I have to POST multiple files with multipart/form-data to a RestAPI-Server, I use ExecuteGroovyScript as described here:

http://apache-nifi-users-list.2361937.n4.nabble.com/POST-multipart-form-data-with-Invokehttp-td9374.html

Now, my NiFi flow should run on a different server and I get:

'GroovyScript' is invalid because ... unresolved dependency: org.apache.httpcomponents#httpmime

I have no admin access to this NiFi-Server and I can't change the NiFi configuration so I can't fix the GroovyScript error.

Is it possible to send multiple files with multipart/form-data only with the InvokeHttp processor?

(I didn't find any working solution with Google)