WIP Group contributions by URL

app/models/contribution.js

@@ -2,6 +2,8 @@ import EmberObject, { computed } from '@ember/object';
 import { isEmpty, isPresent } from '@ember/utils';
 import moment from 'moment';
 
+import contributionGroupingKey from 'kredits-web/utils/contribution-grouping-key';
+
 export default EmberObject.extend({
   // Contract
   id: null,
@@ -44,6 +46,13 @@ export default EmberObject.extend({
     return isPresent(this.pendingTx);
   }),
 
+  // Stable key shared by all per-contributor contributions created for the
+  // same issue/pull request (derived from `url`). Manual contributions without
+  // a URL return null and are treated as singletons (not grouped).
+  groupId: computed('url', function() {
+    return contributionGroupingKey(this);
+  }),
+
   serialize () {
     return JSON.stringify(this);
   }