Add watchtower metadata (#635)

app/controllers/application_controller.rb

@@ -106,6 +106,7 @@ class ApplicationController < ActionController::Base
       meeting_logout_url: request.base_url + logout_room_path(@room),
       meeting_recorded: true,
       moderator_message: "#{invite_msg}\n\n#{request.base_url + room_path(@room)}",
+      host: request.host,
       recording_default_visibility: Setting.find_or_create_by!(provider: user_settings_provider)
                                            .get_value("Default Recording Visibility") == "public"
     }