FIX: Support idempotent admin notice dismissal (#29099)

If you have the admin dashboard open, and one of the admin notices listed has already been dismissed (e.g. in another tab, or by another admin) we would show an ugly "FAILED" modal.

This change makes the admin dismiss endpoint idempotent. If the admin notice is already destroyed, then respond with 200. This will also correctly remove it from the list in the front-end.

app/services/admin_notices/dismiss.rb

@@ -3,7 +3,7 @@
 class AdminNotices::Dismiss
   include Service::Base
 
-  model :admin_notice
+  model :admin_notice, optional: true
 
   policy :invalid_access
 
@@ -23,10 +23,14 @@ class AdminNotices::Dismiss
   end
 
   def destroy(admin_notice:)
+    return if admin_notice.blank?
+
     admin_notice.destroy!
   end
 
   def reset_problem_check(admin_notice:)
+    return if admin_notice.blank?
+
     ProblemCheckTracker.find_by(identifier: admin_notice.identifier)&.reset
   end
 end

spec/services/admin_notices/dismiss_spec.rb

@@ -12,6 +12,14 @@ RSpec.describe(AdminNotices::Dismiss) do
     it { is_expected.to fail_a_policy(:invalid_access) }
   end
 
+  context "when the admin notice has already been dismissed" do
+    fab!(:current_user) { Fabricate(:admin) }
+
+    before { admin_notice.destroy! }
+
+    it { is_expected.to run_successfully }
+  end
+
   context "when user is allowed to perform the action" do
     fab!(:current_user) { Fabricate(:admin) }