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

* Add ability to purge undeliverable domains from admin interface

* Add tests

spec/services/purge_domain_service_spec.rb

@@ -0,0 +1,27 @@
+require 'rails_helper'
+
+RSpec.describe PurgeDomainService, type: :service do
+  let!(:old_account) { Fabricate(:account, domain: 'obsolete.org') }
+  let!(:old_status1) { Fabricate(:status, account: old_account) }
+  let!(:old_status2) { Fabricate(:status, account: old_account) }
+  let!(:old_attachment) { Fabricate(:media_attachment, account: old_account, status: old_status2, file: attachment_fixture('attachment.jpg')) }
+
+  subject { PurgeDomainService.new }
+
+  describe 'for a suspension' do
+    before do
+      subject.call('obsolete.org')
+    end
+
+    it 'removes the remote accounts\'s statuses and media attachments' do
+      expect { old_account.reload }.to raise_exception ActiveRecord::RecordNotFound
+      expect { old_status1.reload }.to raise_exception ActiveRecord::RecordNotFound
+      expect { old_status2.reload }.to raise_exception ActiveRecord::RecordNotFound
+      expect { old_attachment.reload }.to raise_exception ActiveRecord::RecordNotFound
+    end
+
+    it 'refreshes instances view' do
+      expect(Instance.where(domain: 'obsolete.org').exists?).to be false
+    end
+  end
+end