delete http://api.vr-pay-secure.de/v1.0/Invoice//
Response
xxxxxxxxxx
apiSignature=`echo -n "" | openssl dgst -sha256 -hmac "INSTANCE_API_SECRET" -binary | openssl enc -base64`
curl --request DELETE "https://api.vr-pay-secure.de/v1.0/Invoice/1/?instance=INSTANCE_NAME" --data-urlencode "ApiSignature=$apiSignature"