feat(mail): devise mailer respect user preferred host for any mail

app/mailers/devise_user_mailer.rb

@@ -10,11 +10,22 @@ class DeviseUserMailer < Devise::Mailer
   include PriorityDeliveryConcern
 
   layout 'mailers/layout'
+  default from: "#{APPLICATION_NAME} <#{CONTACT_EMAIL}>"
 
   def template_paths
     ['devise_mailer']
   end
 
+  # Note: this devise hook (like any callback) is called *after* the action,
+  # because we use mailers with Mailer.action_name() syntax
+  # instead of parameterized Mailer.with().action_name.
+  # So any action using Current must manually call `configure_defaults_for_user`
+  def initialize_from_record(record)
+    configure_defaults_for_user(record)
+
+    super
+  end
+
   def confirmation_instructions(record, token, opts = {})
     configure_defaults_for_user(record)
 

spec/mailers/devise_user_mailer_spec.rb

@@ -44,6 +44,26 @@ RSpec.describe DeviseUserMailer, type: :mailer do
         end
       end
     end
+
+    context "reset password instructions" do
+      subject { described_class.reset_password_instructions(user, token) }
+
+      context "legacy domain" do
+        it "respect preferred domain" do
+          expect(header_value("From", subject.message)).to include(CONTACT_EMAIL)
+          expect(subject.message.to_s).to include("#{ENV.fetch("APP_HOST_LEGACY")}/users/password")
+        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 include("@demarches.gouv.fr")
+          expect(subject.message.to_s).to include("#{ENV.fetch("APP_HOST")}/users/password")
+        end
+      end
+    end
   end
 
   def header_value(name, message)