Preventing users from buying already gifted subscriber items (#7734)

* Adding the unopened mystery items to the call to get not obtained subscriber items. closes #7712

* refactoring according to pr

* Refactoring according to pr. moved time-travelers to it's own file and added new tests.

website/common/script/content/time-travelers.js

@@ -0,0 +1,31 @@
+import _ from 'lodash';
+import mysterySets from './mystery-sets';
+import gear from './gear';
+
+let mystery = mysterySets;
+
+_.each(mystery, (v, k) => {
+  return v.items = _.where(gear.flat, {
+    mystery: k,
+  });
+});
+
+let timeTravelerStore = (user) => {
+  let ownedKeys;
+  let owned = user.items.gear.owned;
+  let unopenedGifts = user.purchased.plan.mysteryItems;
+  ownedKeys = _.keys((typeof owned.toObject === 'function' ? owned.toObject() : undefined) || owned);
+  ownedKeys = _.union(ownedKeys, unopenedGifts);
+  return _.reduce(mystery, (m, v, k) => {
+    if (k === 'wondercon' || ownedKeys.indexOf(v.items[0].key) !== -1) {
+      return m;
+    }
+    m[k] = v;
+    return m;
+  }, {});
+};
+
+module.exports = {
+  timeTravelerStore,
+  mystery,
+};