private void checkAndCopyUserDefs(Bundle bundle, List<Bundle> bundlesAdded) throws IOException {
        for (Bundle.DefEntry def : bundle.getDefEntries()) {
            checkUserDefConflict(bundle, def, bundlesAdded);
            String defFilename = def.defNamespace + "." + def.defName + ".def";
            OutputStream out = new FileOutputStream(new File(defDir, defFilename));
            out.write(def.contents.getBytes());
            out.close();
        }
    }
A @{link ConfigDefinitionDir} contains a set of config definitions. New definitions may be added,
but they cannot conflict with the existing ones.

@author Ulf Lilleengen
config-application-package/src/main/java/com/yahoo/config/application/ConfigDefinitionDir.java