Add system checks to dashboard in admin UI (#15989)

app/views/admin/dashboard/index.html.haml

@@ -1,6 +1,14 @@
 - content_for :page_title do
   = t('admin.dashboard.title')
 
+- unless @system_checks.empty?
+  .flash-message-stack
+    - @system_checks.each do |message|
+      .flash-message.warning
+        = t("admin.system_checks.#{message.key}.message_html", message.value ? { value: content_tag(:strong, message.value) } : {})
+        - if message.action
+          = link_to t("admin.system_checks.#{message.key}.action"), message.action
+
 .dashboard__counters
   %div
     = link_to admin_accounts_url(local: 1, recent: 1) do