Create a new method to change the lang of the app

- The old method (link to `?locale=#{l.to_s}`) was not functional for path that already has query params in current path (such as `/user/spree_user/password/edit?reset_password_token=`) ;
 - This seems that the best way to handle this, is to create a new route, new method that effectively set the lang (not the locale actually...) and then redirect_back (ie. using the HTTP_REFERER, with a fallback to `/`)

s

app/controllers/locales_controller.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class LocalesController < BaseController
+  def show
+    UserLocaleSetter.new(spree_current_user, params[:id], cookies).set_locale
+    redirect_back fallback_location: main_app.root_url
+  end
+end

app/views/shared/menu/_language_selector.html.haml

@@ -5,4 +5,4 @@
   %ul.dropdown
     - OpenFoodNetwork::I18nConfig.selectable_locales.each do |l|
       %li
-        %a{href: "?locale=#{l.to_s}" }= t('language_name', locale: l)
+        = link_to t('language_name', locale: l), main_app.locale_path(l.to_s)

config/routes.rb

@@ -20,6 +20,7 @@ Openfoodnetwork::Application.routes.draw do
   get "/register", to: "registration#index", as: :registration
   get "/register/auth", to: "registration#authenticate", as: :registration_auth
   post "/user/registered_email", to: "spree/users#registered_email"
+  resources :locales, only: [:show]
 
   # Redirects to global website
   get "/connect", to: redirect("https://openfoodnetwork.org/#{ENV['DEFAULT_COUNTRY_CODE'].andand.downcase}/connect/")

spec/features/consumer/multilingual_spec.rb

@@ -127,11 +127,11 @@ feature 'Multilingual', js: true do
 
         find('.language-switcher').click
         within '.language-switcher .dropdown' do
-          expect(page).to have_link I18n.t('language_name', locale: :en), href: '?locale=en'
+          expect(page).to have_link I18n.t('language_name', locale: :en), href: '/locales/en'
           expect(page).to have_link I18n.t('language_name', locale: :es, default: 'Language Name'),
-                                    href: '?locale=es'
+                                    href: '/locales/es'
 
-          find('li a[href="?locale=es"]').click
+          find('li a[href="/locales/es"]').click
         end
 
         expect_menu_and_cookie_in_es