Add ability to purge undeliverable domains from admin interface (#16686)

* Add ability to purge undeliverable domains from admin interface

* Add tests

spec/workers/admin/domain_purge_worker_spec.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Admin::DomainPurgeWorker do
+  subject { described_class.new }
+
+  describe 'perform' do
+    it 'calls domain purge service for relevant domain block' do
+      service = double(call: nil)
+      allow(PurgeDomainService).to receive(:new).and_return(service)
+      result = subject.perform('example.com')
+
+      expect(result).to be_nil
+      expect(service).to have_received(:call).with('example.com')
+    end
+  end
+end