Use expect for nested params in settings/* controllers (#33673)

spec/requests/settings/migration/redirects_spec.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Settings Migration Redirects' do
+  describe 'POST /settings/migration/redirect' do
+    before { sign_in Fabricate(:user) }
+
+    it 'gracefully handles invalid nested params' do
+      post settings_migration_redirect_path(form_redirect: 'invalid')
+
+      expect(response)
+        .to have_http_status(400)
+    end
+  end
+end