added 260907 version of worker toolkit

worker-toolkit-flaredown/repo/frontend/app/mixins/nested-destroyable.js

@@ -0,0 +1,12 @@
+import DS from 'ember-data';
+import Ember from 'ember';
+
+export default Ember.Mixin.create({
+
+  _destroy: DS.attr('string'),
+  prepareForDestroy: function() {
+    this.set('_destroy', '1');
+  },
+  isPreparedForDestroy: Ember.computed.equal('_destroy', '1')
+
+});