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

* Add ability to purge undeliverable domains from admin interface

* Add tests

app/services/purge_domain_service.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class PurgeDomainService < BaseService
+  def call(domain)
+    Account.remote.where(domain: domain).reorder(nil).find_each do |account|
+      DeleteAccountService.new.call(account, reserve_username: false, skip_side_effects: true)
+    end
+    Instance.refresh
+  end
+end