Extract the locale helpers to a dedicated namespace

admin/app/controllers/solidus_admin/base_controller.rb

@@ -6,28 +6,14 @@ module SolidusAdmin
   class BaseController < ApplicationController
     include ActiveStorage::SetCurrent
     include Spree::Core::ControllerHelpers::Store
-    include Spree::Admin::SetsUserLanguageLocaleKey
     include GearedPagination::Controller
 
     include SolidusAdmin::ControllerHelpers::Auth
+    include SolidusAdmin::ControllerHelpers::Locale
     include SolidusAdmin::AuthAdapters::Backend if defined?(Spree::Backend)
 
-
-    before_action :set_locale
-
     layout 'solidus_admin/application'
     helper 'solidus_admin/container'
     helper 'solidus_admin/layout'
-
-    private
-
-    def set_locale
-      if params[:switch_to_locale].to_s != session[set_user_language_locale_key].to_s
-        session[set_user_language_locale_key] = params[:switch_to_locale]
-        flash[:notice] = t('spree.locale_changed')
-      end
-
-      I18n.locale = session[set_user_language_locale_key] ? session[set_user_language_locale_key].to_sym : I18n.default_locale
-    end
   end
 end

admin/app/controllers/solidus_admin/controller_helpers/locale.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module SolidusAdmin::ControllerHelpers::Locale
+  extend ActiveSupport::Concern
+  include Spree::Admin::SetsUserLanguageLocaleKey
+
+  included do
+    before_action :set_locale
+  end
+
+  private
+
+  def set_locale
+    if params[:switch_to_locale].to_s != session[set_user_language_locale_key].to_s
+      session[set_user_language_locale_key] = params[:switch_to_locale]
+      flash[:notice] = t('spree.locale_changed')
+    end
+
+    I18n.locale = session[set_user_language_locale_key] ? session[set_user_language_locale_key].to_sym : I18n.default_locale
+  end
+end