create bookmark serializer

apps/app/src/server/models/serializers/bookmark-serializer.js

@@ -0,0 +1,25 @@
+const { serializePageSecurely } = require('./page-serializer');
+
+function serializeInsecurePageAttributes(bookmark) {
+  if (bookmark.page != null && bookmark.page._id != null) {
+    bookmark.page = serializePageSecurely(bookmark.page);
+  }
+  return bookmark;
+}
+
+function serializeBookmarkSecurely(bookmark) {
+  let serialized = bookmark;
+
+  // invoke toObject if bookmark is a model instance
+  if (bookmark.toObject != null) {
+    serialized = bookmark.toObject();
+  }
+
+  serializeInsecurePageAttributes(serialized);
+
+  return serialized;
+}
+
+module.exports = {
+  serializeBookmarkSecurely,
+};