docs: public void parsePropertyCustomExtensions(ActivityImpl activity, Element propertyElement, String propertyName, String propertyType) {
  
      if (propertyType == null) {
        String type = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, TYPE);
        propertyType = type != null ? type : "string"; // default is string
      }
  
      VariableDeclaration variableDeclaration = new VariableDeclaration(propertyName, propertyType);
      addVariableDeclaration(activity, variableDeclaration);
      activity.setScope(true);
  
      String src = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "src");
      if (src != null) {
        variableDeclaration.setSourceVariableName(src);
      }
  
      String srcExpr = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "srcExpr");
      if (srcExpr != null) {
        Expression sourceExpression = expressionManager.createExpression(srcExpr);
        variableDeclaration.setSourceExpression(sourceExpression);
      }
  
      String dst = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "dst");
      if (dst != null) {
        variableDeclaration.setDestinationVariableName(dst);
      }
  
      String destExpr = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "dstExpr");
      if (destExpr != null) {
        Expression destinationExpression = expressionManager.createExpression(destExpr);
        variableDeclaration.setDestinationExpression(destinationExpression);
      }
  
      String link = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "link");
      if (link != null) {
        variableDeclaration.setLink(link);
      }
  
      String linkExpr = propertyElement.attributeNS(CAMUNDA_BPMN_EXTENSIONS_NS, "linkExpr");
      if (linkExpr != null) {
        Expression linkExpression = expressionManager.createExpression(linkExpr);
        variableDeclaration.setLinkExpression(linkExpression);
      }
  
      for (BpmnParseListener parseListener : parseListeners) {
        parseListener.parseProperty(propertyElement, variableDeclaration, activity);
      }
    }