use env for maintenance mode to avoid DB roundtrip

app/controllers/application_controller.rb

@@ -11,7 +11,7 @@ class ApplicationController < ActionController::Base
   before_action :set_current_roles
   before_action :set_sentry_user
   before_action :redirect_if_untrusted
-  before_action :reject, if: -> { feature_enabled?(:maintenance_mode) }
+  before_action :reject, if: -> { ENV.fetch("MAINTENANCE_MODE", 'false') == 'true' }
   before_action :configure_permitted_parameters, if: :devise_controller?
 
   before_action :staging_authenticate

config/env.example.optional

@@ -67,3 +67,5 @@ DS_ENV="staging"
 # Personnalisation d'instance - fichier utilisé pour poser un filigrane sur les pièces d'identité
 # WATERMARK_FILE=""
 
+# Active le mode maintenance
+# MAINTENANCE_MODE="true"

config/initializers/flipper.rb

@@ -34,7 +34,6 @@ features = [
   :insee_api_v3,
   :instructeur_bypass_email_login_token,
   :localization,
-  :maintenance_mode,
   :make_experts_notifiable,
   :mini_profiler,
   :procedure_routage_api,