docs: private Element migrate(Element root) {
          if (root.getAttributeNode(PLUGIN_VERSION_ATTR) == null) {
              final List<Element> features = toList(root.getElementsByTagName(FEATURE_ELEM));
              final String version = features.stream()
                      .filter(elem -> elem.getAttribute(FEATURE_ID_ATTR).equals("package.version"))
                      .findFirst()
                      .map(elem -> elem.getAttribute(FEATURE_VALUE_ATTR))
                      .orElse("0.0.0");
              root.setAttribute(PLUGIN_VERSION_ATTR, version);
          }
          return root;
      }