Fix last update time for project in group page

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/349310
Changelog: fixed

app/assets/javascripts/groups/components/item_stats.vue

@@ -83,7 +83,7 @@ export default {
       <gl-badge variant="warning">{{ __('pending deletion') }}</gl-badge>
     </div>
     <div v-if="isProject" class="last-updated">
-      <time-ago-tooltip :time="item.updatedAt" tooltip-placement="bottom" />
+      <time-ago-tooltip :time="item.lastActivityAt" tooltip-placement="bottom" />
     </div>
   </div>
 </template>

app/assets/javascripts/groups/store/groups_store.js

@@ -98,6 +98,9 @@ export default class GroupsStore {
       updatedAt: rawGroupItem.updated_at,
       pendingRemoval: rawGroupItem.marked_for_deletion,
       microdata: this.showSchemaMarkup ? getGroupItemMicrodata(rawGroupItem) : {},
+      lastActivityAt: rawGroupItem.last_activity_at
+        ? rawGroupItem.last_activity_at
+        : rawGroupItem.updated_at,
     };
 
     if (!isEmpty(rawGroupItem.compliance_management_framework)) {

app/serializers/group_child_entity.rb

@@ -33,6 +33,8 @@ class GroupChildEntity < Grape::Entity
   end
 
   # Project only attributes
+  expose :last_activity_at, if: lambda { |instance| project? }
+
   expose :star_count, :archived,
          if: lambda { |_instance, _options| project? }
 

spec/frontend/groups/components/group_item_spec.js

@@ -100,6 +100,7 @@ describe('GroupItemComponent', () => {
         wrapper.destroy();
 
         group.type = 'project';
+        group.lastActivityAt = '2017-04-09T18:40:39.101Z';
         wrapper = createComponent({ group });
 
         expect(wrapper.vm.isGroup).toBe(false);

spec/frontend/groups/components/item_stats_spec.js

@@ -38,6 +38,7 @@ describe('ItemStats', () => {
         ...mockParentGroupItem,
         type: ITEM_TYPE.PROJECT,
         starCount: 4,
+        lastActivityAt: '2017-04-09T18:40:39.101Z',
       };
 
       createComponent({ item });

spec/serializers/group_child_entity_spec.rb

@@ -62,6 +62,10 @@ RSpec.describe GroupChildEntity do
       expect(json[:edit_path]).to eq(edit_project_path(object))
     end
 
+    it 'includes the last activity at' do
+      expect(json[:last_activity_at]).to be_present
+    end
+
     it_behaves_like 'group child json'
   end