feat(mail): devise confirmation instructions respect user preferred host

app/mailers/concerns/mailer_headers_configurable_concern.rb

@@ -0,0 +1,26 @@
+module MailerHeadersConfigurableConcern
+  extend ActiveSupport::Concern
+
+  included do
+    def configure_defaults_for_user(user)
+      I18n.locale = user.locale
+
+      if user.preferred_domain_demarches_gouv_fr?
+        Current.application_name = "demarches.gouv.fr"
+        Current.host = ENV.fetch("APP_HOST")
+        Current.contact_email = "contact@demarches.gouv.fr"
+        Current.no_reply_email = NO_REPLY_EMAIL.sub("demarches-simplifiees.fr", "demarches.gouv.fr") # rubocop:disable DS/ApplicationName
+      else
+        Current.application_name = APPLICATION_NAME
+        Current.host = ENV["APP_HOST_LEGACY"] || ENV.fetch("APP_HOST") # _LEGACY is optional, fallbagck to default when unset
+        Current.contact_email = CONTACT_EMAIL
+        Current.no_reply_email = NO_REPLY_EMAIL
+      end
+
+      from = "#{Current.application_name} <#{Current.contact_email}>"
+      self.class.default from: from, reply_to: from
+      self.class.default_url_options = { host: Current.host }
+      self.class.asset_host = Current.application_base_url
+    end
+  end
+end

app/mailers/devise_user_mailer.rb

@@ -5,6 +5,7 @@ class DeviseUserMailer < Devise::Mailer
   include Devise::Controllers::UrlHelpers # Optional. eg. `confirmation_url`
   include MailerDolistConcern
   include MailerMonitoringConcern
+  include MailerHeadersConfigurableConcern
   include BalancedDeliveryConcern
   include PriorityDeliveryConcern
 
@@ -15,7 +16,10 @@ class DeviseUserMailer < Devise::Mailer
   end
 
   def confirmation_instructions(record, token, opts = {})
-    opts[:from] = NO_REPLY_EMAIL
+    configure_defaults_for_user(record)
+
+    opts[:from] = Current.no_reply_email
+    opts[:reply_to] = Current.no_reply_email
     @procedure = opts[:procedure_after_confirmation] || nil
     @prefill_token = opts[:prefill_token]
     super

app/models/current.rb

@@ -1,5 +1,10 @@
 class Current < ActiveSupport::CurrentAttributes
-  attribute :user, :request_id, :browser,
+  attribute :application_base_url
-    :host, :application_name, :contact_email,
+  attribute :application_name
-    :application_base_url
+  attribute :browser
+  attribute :contact_email
+  attribute :host
+  attribute :no_reply_email
+  attribute :request_id
+  attribute :user
 end

spec/mailers/devise_user_mailer_spec.rb

@@ -16,8 +16,37 @@ RSpec.describe DeviseUserMailer, type: :mailer do
 
     context 'when perform_later is called' do
       it 'enqueues email in default queue for high priority delivery' do
-  expect { subject.deliver_later }.to have_enqueued_job.on_queue(Rails.application.config.action_mailer.deliver_later_queue_name)
+        expect { subject.deliver_later }.to have_enqueued_job.on_queue(Rails.application.config.action_mailer.deliver_later_queue_name)
-end
+      end
     end
   end
+
+  describe 'headers for user' do
+    context "confirmation email" do
+      subject { described_class.confirmation_instructions(user, token, opts = {}) }
+
+      context "legacy domain" do
+        it "respect preferred domain" do
+          expect(header_value("From", subject.message)).to eq(NO_REPLY_EMAIL)
+          expect(header_value("Reply-To", subject.message)).to eq(NO_REPLY_EMAIL)
+          expect(subject.message.to_s).to include("#{ENV.fetch("APP_HOST_LEGACY")}/users/confirmation")
+        end
+      end
+
+      context "new domain" do
+        let(:user) { create(:user, preferred_domain: :demarches_gouv_fr) }
+
+        it "respect preferred domain" do
+          expect(header_value("From", subject.message)).to eq("Ne pas répondre <ne-pas-repondre@demarches.gouv.fr>")
+          expect(header_value("Reply-To", subject.message)).to eq("Ne pas répondre <ne-pas-repondre@demarches.gouv.fr>")
+          expect(subject.message.to_s).to include("#{ENV.fetch("APP_HOST")}/users/confirmation")
+          expect(subject.message.to_s).to include("//#{ENV.fetch("APP_HOST")}/assets/mailer/republique")
+        end
+      end
+    end
+  end
+
+  def header_value(name, message)
+    message.header.fields.find { _1.name == name }.value
+  end
 end