B1iF Http PATCH request Body

Hello Guys,

i need help with a scenario im developing right now.

I have a scenario where i automatically get Invoices from a standalone API and importing them into B1. After importing i want to write back the DocEntry of the successfully imported invoice.
I have to do a PATCH-request with following information in the body (it needs to look like this or it wont work):

{"sapID":3}

This needs to be in the raw body(JSON) of the PATCH-request.

My Payload in the HTTP-Atom looks like this:

<pltype>json</pltype>

<payload>

<number name="sapID">2</number>

</payload>

<htta> <par id="httpheader.???" value="">

<par id="httpheader.Content-Type" value="application/json">

</par>

<!--optional - you can specify here your own http header definitions - multiple elements allowed-->

</par>

<par id="htta.returnpltypeforce" value="json">

<!--optional-->

</par>

<par id="htta.returnpltypedefault" value="json">

<!--optional-->

</par>

</htta>

When i look onto my API, the body sent is empty. Meaning that something is wrong with my payload. Is there anyway i can specify the body and directly send my information in said (raw) body?