Ensure datetime/date are serialized to correct format (#33086)

spec/serializers/rest/admin/email_domain_block_serializer_spec.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe REST::Admin::EmailDomainBlockSerializer do
+  subject { serialized_record_json(record, described_class) }
+
+  let(:record) { Fabricate(:email_domain_block) }
+
+  context 'when created_at is populated' do
+    it 'parses as RFC 3339 datetime' do
+      expect { DateTime.rfc3339(subject['created_at']) }.to_not raise_error
+    end
+  end
+end