docs: public T payload(Object payload, Marshaller marshaller) {
          StringResult result = new StringResult();
  
          try {
              marshaller.marshal(payload, result);
          } catch (XmlMappingException e) {
              throw new CitrusRuntimeException("Failed to marshal object graph for message payload", e);
          } catch (IOException e) {
              throw new CitrusRuntimeException("Failed to marshal object graph for message payload", e);
          }
  
          setPayload(result.toString());
  
          return self;
      }