feat(admin): notify registrar about domain status changes

- Add inform_registrar_about_status_changes method to detect added and removed statuses after domain update.
- Send notification to registrar with details of which statuses were set and which were removed.
- Integrate notification logic into domain update action.

app/controllers/admin/domains_controller.rb

@@ -31,6 +31,7 @@ module Admin
 
       if @domain.update(dp)
         flash[:notice] = I18n.t('domain_updated')
+        inform_registrar_about_status_changes
         redirect_to [:admin, @domain]
       else
         @domain.reload
@@ -111,6 +112,20 @@ module Admin
       end
     end
 
+    def inform_registrar_about_status_changes
+      return unless @domain.saved_change_to_statuses?
+
+      old_statuses, new_statuses = @domain.saved_change_to_statuses
+      removed = old_statuses - new_statuses
+      added   = new_statuses - old_statuses
+  
+      msg = []
+      msg << "Set on #{@domain.name}: #{added.join(', ')}" unless added.empty?
+      msg << "Removed from #{@domain.name}: #{removed.join(', ')}" unless removed.empty?
+
+      @domain.registrar.notifications.create!(text: msg.join('. ')) if msg.any?
+    end
+
     def build_associations
       @server_statuses = @domain.statuses.select { |x| DomainStatus::SERVER_STATUSES.include?(x) }
       @server_statuses = [nil] if @server_statuses.empty?