Add group-level callout for disabled webhooks

What does this MR do and why?

• This adds the frontend code for a group-wide alert (visible to owner / maintainer) when a webhook fails for some reason.
• Once a user dismisses it, it should not show again (persistent user callout functionality).
• The alert does not show on the webhook page itself or on the webhook logs page.

Changelog: changed

EE: true

There is a similar MR for the project-level alert !95998 (merged).

Screenshots or screen recordings

How to set up and validate locally

1. Go to Group > Settings > Webhook and create a webhook (you can use any valid URL).
2. Mark the webhook as temporary disabled by running this in your bin/rails console:

g = GroupHook.last
g.recent_failures = 5
g.disabled_until = Time.now + 1.month
g.save

3. Force show the alert with this diff:

diff --git a/app/models/users/group_callout.rb b/app/models/users/group_callout.rb
index 2552407fa4cd..1e2afdc28d51 100644
--- a/app/models/users/group_callout.rb
+++ b/app/models/users/group_callout.rb
@@ -24,7 +24,8 @@ class GroupCallout < ApplicationRecord
       namespace_storage_limit_banner_error_threshold: 13, # EE-only
       usage_quota_trial_alert: 14, # EE-only
       preview_usage_quota_free_plan_alert: 15, # EE-only
-      enforcement_at_limit_alert: 16 # EE-only
+      enforcement_at_limit_alert: 16, # EE-only
+      web_hook_disabled: 17 # EE-only
     }
 
     validates :group, presence: true
diff --git a/ee/app/helpers/ee/web_hooks/web_hooks_helper.rb b/ee/app/helpers/ee/web_hooks/web_hooks_helper.rb
index 494bc362fe6e..20759559f899 100644
--- a/ee/app/helpers/ee/web_hooks/web_hooks_helper.rb
+++ b/ee/app/helpers/ee/web_hooks/web_hooks_helper.rb
@@ -42,7 +42,7 @@ def show_group_hook_failed_callout?(group)
         return false if group_hook_page?
         return false unless current_user
 
-        false # More conditions / logic to be added before showing this callout
+        true # More conditions / logic to be added before showing this callout
       end
 
       def group_hook_page?

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #385902 (closed)