refactor(mailer): for devise mailer set locale in dedicated action

app/mailers/concerns/mailer_defaults_configurable_concern.rb

@@ -32,8 +32,6 @@ module MailerDefaultsConfigurableConcern
     def configure_defaults_for_user(user)
       return if !user.is_a?(User) # not for super-admins
 
-      I18n.locale = user.locale
-
       if user.preferred_domain_demarches_gouv_fr?
         set_currents_for_demarches_gouv_fr
       else

app/mailers/devise_user_mailer.rb

@@ -33,7 +33,10 @@ class DeviseUserMailer < Devise::Mailer
     opts[:reply_to] = Current.no_reply_email
     @procedure = opts[:procedure_after_confirmation] || nil
     @prefill_token = opts[:prefill_token]
-    super
+
+    I18n.with_locale(record.locale) do
+      super
+    end
   end
 
   def self.critical_email?(action_name)

spec/mailers/devise_user_mailer_spec.rb

@@ -19,6 +19,24 @@ RSpec.describe DeviseUserMailer, type: :mailer do
         expect { subject.deliver_later }.to have_enqueued_job.on_queue(Rails.application.config.action_mailer.deliver_later_queue_name)
       end
     end
+
+    describe "i18n" do
+      context "when locale is fr" do
+        let(:user) { create(:user, locale: :fr) }
+
+        it "uses fr locale" do
+          expect(subject.body).to include("Activez votre compte")
+        end
+      end
+
+      context "when locale is en" do
+        let(:user) { create(:user, locale: :en) }
+
+        it "uses en locale" do
+          expect(subject.body).to include("Activate account")
+        end
+      end
+    end
   end
 
   describe 'headers for user' do