Add enable duo banner for self-managed

What does this MR do and why?

Related to #536440

Add the enable duo banner for self-managed instances

dot com version here: !188312 (merged)

References

Screenshots or screen recordings

Admin dashboard	Admin Duo setting

Dismissing one doesn't affect the other banner	Enabling Duo Core dismisses both banners
Screen_Recording_2025-04-28_at_3.15.13_PM	Screen_Recording_2025-04-28_at_3.15.30_PM

How to set up and validate locally

1. Make sure your local GDK has a license and not simulating SaaS: https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/main/doc/setup/gitlab.md#adding-a-license-from-staging-customers-portal-to-your-gdk
2. Comment out the date condition by applying this diff:

Click to expand

diff --git a/ee/app/helpers/ee/users/callouts_helper.rb b/ee/app/helpers/ee/users/callouts_helper.rb
index b585a78c9860..0ad1938e6914 100644
--- a/ee/app/helpers/ee/users/callouts_helper.rb
+++ b/ee/app/helpers/ee/users/callouts_helper.rb
@@ -74,8 +74,8 @@ def show_transition_to_jihu_callout?
       end

       def show_enable_duo_banner_sm?(callouts_feature_name)
-        Date.current >= DUO_CORE_RELEASE_DATE &&
-          ::Feature.enabled?(:allow_duo_base_access, :instance) &&
+        # Date.current >= DUO_CORE_RELEASE_DATE &&
+        ::Feature.enabled?(:allow_duo_base_access, :instance) &&
           ::Feature.enabled?(:show_enable_duo_banner_sm, :instance) &&
           current_user.can_admin_all_resources? &&
           License.duo_core_features_available? &&

3. Enable feature flag in rails console: Feature.enable(:allow_duo_base_access)
4. Sign in as admin
5. Visit /admin and /admin/gitlab_duo to see the banners.

MR acceptance checklist

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