feat: Upgrade page instead of banner (#11202)

# Pull Request Template

## Description

This PR will replace the upgrade banner with an upgrade page view.

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

### Loom video

https://www.loom.com/share/0f2b4b09acdd4404bf3211184a470227?sid=7ed60a99-0299-4642-b907-2af8c4dcc643


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Pranav <pranavrajs@gmail.com>

enterprise/app/controllers/enterprise/api/v1/accounts_controller.rb

@@ -13,24 +13,24 @@ class Enterprise::Api::V1::AccountsController < Api::BaseController
   end
 
   def limits
-    limits = {
-      'conversation' => {},
-      'non_web_inboxes' => {},
-      'captain' => @account.usage_limits[:captain]
-    }
-
-    if default_plan?(@account)
-      limits = {
-        'conversation' => {
-          'allowed' => 500,
-          'consumed' => conversations_this_month(@account)
-        },
-        'non_web_inboxes' => {
-          'allowed' => 0,
-          'consumed' => non_web_inboxes(@account)
-        }
-      }
-    end
+    limits = if default_plan?(@account)
+               {
+                 'conversation' => {
+                   'allowed' => 500,
+                   'consumed' => conversations_this_month(@account)
+                 },
+                 'non_web_inboxes' => {
+                   'allowed' => 0,
+                   'consumed' => non_web_inboxes(@account)
+                 },
+                 'agents' => {
+                   'allowed' => 2,
+                   'consumed' => agents(@account)
+                 }
+               }
+             else
+               default_limits
+             end
 
     # include id in response to ensure that the store can be updated on the frontend
     render json: { id: @account.id, limits: limits }, status: :ok
@@ -49,6 +49,15 @@ class Enterprise::Api::V1::AccountsController < Api::BaseController
 
   private
 
+  def default_limits
+    {
+      'conversation' => {},
+      'non_web_inboxes' => {},
+      'agents' => {},
+      'captain' => @account.usage_limits[:captain]
+    }
+  end
+
   def fetch_account
     @account = current_user.accounts.find(params[:id])
     @current_account_user = @account.account_users.find_by(user_id: current_user.id)