Fix removing allowed domains being done synchronously (#14302)

* Fix removing allowed domains being done synchronously

* Add tests

app/services/after_unallow_domain_service.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AfterUnallowDomainService < BaseService
+  def call(domain)
+    Account.where(domain: domain).find_each do |account|
+      SuspendAccountService.new.call(account, reserve_username: false)
+    end
+  end
+end