Implement Instance Moderation Notes (#31529)

spec/requests/admin/instances/moderation_notes_spec.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin Report Notes' do
+  describe 'POST /admin/instance/moderation_notes' do
+    before { sign_in Fabricate(:admin_user) }
+
+    it 'gracefully handles invalid nested params' do
+      post admin_instance_moderation_notes_path(instance_id: 'mastodon.test', instance_note: 'invalid')
+
+      expect(response)
+        .to have_http_status(400)
+    end
+  end
+end