refactor: 💡 model grants as a fragment-array for statefulness

addons/api/addon/models/fragment-string.js

@@ -0,0 +1,16 @@
+import Fragment from 'ember-data-model-fragments/fragment';
+import { attr } from '@ember-data/model';
+
+/**
+ * Represents an item in an array of strings.
+ */
+export default class FragmentStringModel extends Fragment {
+
+  // =attributes
+
+  @attr('string', {
+    description: 'The value of the string.'
+  })
+  value;
+
+}

addons/api/addon/models/role.js

@@ -1,5 +1,5 @@
 import GeneratedRoleModel from '../generated/models/role';
-import { array } from 'ember-data-model-fragments/attributes';
+import { fragmentArray } from 'ember-data-model-fragments/attributes';
 
 export default class RoleModel extends GeneratedRoleModel {
 
@@ -9,7 +9,7 @@ export default class RoleModel extends GeneratedRoleModel {
    * Grants is read-only _most_ under normal circumstances.  But grants can
    * be persisted via a dedicated call to `saveGrants()`.
    */
-  @array({readOnly: true}) grants;
+  @fragmentArray('fragment-string', {readOnly: true}) grants;
 
   // =methods