fix: Improve performance of most hit APIs in widget (#11089)

- Cache campaigns for better performance
- Fix N+1 queries in inbox members
- Remove unused related articles

app/javascript/widget/store/modules/specs/campaign/actions.spec.js

@@ -63,15 +63,37 @@ describe('#actions', () => {
     };
     it('sends correct actions if campaigns are empty', async () => {
       await actions.initCampaigns(
-        { dispatch, getters: { getCampaigns: [] } },
+        {
+          dispatch,
+          getters: { getCampaigns: [], getUIFlags: { hasFetched: false } },
+        },
         actionParams
       );
       expect(dispatch.mock.calls).toEqual([['fetchCampaigns', actionParams]]);
       expect(campaignTimer.initTimers).not.toHaveBeenCalled();
     });
+
+    it('do not refetch if the campaigns are fetched once', async () => {
+      await actions.initCampaigns(
+        {
+          dispatch,
+          getters: { getCampaigns: [], getUIFlags: { hasFetched: true } },
+        },
+        actionParams
+      );
+      expect(dispatch.mock.calls).toEqual([]);
+      expect(campaignTimer.initTimers).not.toHaveBeenCalled();
+    });
+
     it('resets time if campaigns are available', async () => {
       await actions.initCampaigns(
-        { dispatch, getters: { getCampaigns: campaigns } },
+        {
+          dispatch,
+          getters: {
+            getCampaigns: campaigns,
+            getUIFlags: { hasFetched: true },
+          },
+        },
         actionParams
       );
       expect(dispatch.mock.calls).toEqual([]);