feat: Throttle meta request for large chat size (#10518)

For large accounts with huge volumes of messages, it can be very
wasteful to make the meta request so often. It also puts un-necessary
load on the DB bombarding it with so many requests. This PR fixes it by
throttling the requests to 5 seconds for all users with more than 1000
accessible chats.

### Why not cache this value in the backend?

Well, it's a bit tricky, since a user can have different permissions
over inboxes and can see different chats, maintaining a cache for each
of them is not effective, besides the requests will reach the server
anyway.

app/javascript/dashboard/store/modules/specs/conversationStats/actions.spec.js

@@ -11,7 +11,7 @@ describe('#actions', () => {
     it('sends correct mutations if API is success', async () => {
       axios.get.mockResolvedValue({ data: { meta: { mine_count: 1 } } });
       await actions.get(
-        { commit },
+        { commit, state: { updatedOn: null } },
         { inboxId: 1, assigneeTpe: 'me', status: 'open' }
       );
       expect(commit.mock.calls).toEqual([
@@ -21,7 +21,7 @@ describe('#actions', () => {
     it('sends correct actions if API is error', async () => {
       axios.get.mockRejectedValue({ message: 'Incorrect header' });
       await actions.get(
-        { commit },
+        { commit, state: { updatedOn: null } },
         { inboxId: 1, assigneeTpe: 'me', status: 'open' }
       );
       expect(commit.mock.calls).toEqual([]);

app/javascript/dashboard/store/modules/specs/conversationStats/mutations.spec.js

@@ -14,6 +14,7 @@ describe('#mutations', () => {
         mineCount: 1,
         unAssignedCount: 1,
         allCount: 2,
+        updatedOn: expect.any(Date),
       });
     });
   });