What is the best way to parse MadExcept bugreports sent to a datasnap server?

Question

I configured a datasnap rest server as a custom script upload location for madexcept.

Everything works fine up to the part where I try to parse the variables set in the report. They were added with

MESettings.AdditionalFields.Add('appname', '%appname%')

I recognized that the report is sent as multipart/form-data, therefore I tried including Web.ReqMulti into my unit to get the parsed with TMultipartContentParser It looks like this in the REST-method

function V1RestMethod.UpdateBugReport: TJSONArray;
var
  LReq:TWebRequest; 
  LAppName:string;   
begin
  LReq:=GetDataSnapWebModule.Request;
  LAppName:= LReq.ContentFields.Values['appname'];  
end;

At this point, LAppName is empty since LReq.ContentFields.Count is 0

What would be the recommended way of parsing this bugreport?

Update_1:

It seems that the TMultipartContentParser seems to correctly parse all files (application/octet-stream) but leaves the plaintext unparsed.