profile: send an email when the account is already taken

spec/mailers/previews/user_mailer_preview.rb

@@ -3,6 +3,10 @@ class UserMailerPreview < ActionMailer::Preview
     UserMailer.new_account_warning(user)
   end
 
+  def account_already_taken
+    UserMailer.account_already_taken(user, 'dircab@territoires.gouv.fr')
+  end
+
   private
 
   def user

spec/mailers/user_mailer_spec.rb

@@ -0,0 +1,21 @@
+require "rails_helper"
+
+RSpec.describe UserMailer, type: :mailer do
+  let(:user) { build(:user) }
+
+  describe '.new_account_warning' do
+    subject { described_class.new_account_warning(user) }
+
+    it { expect(subject.to).to eq([user.email]) }
+    it { expect(subject.body).to include(user.email) }
+  end
+
+  describe '.account_already_taken' do
+    let(:requested_email) { 'new@exemple.fr' }
+
+    subject { described_class.account_already_taken(user, requested_email) }
+
+    it { expect(subject.to).to eq([requested_email]) }
+    it { expect(subject.body).to include(requested_email) }
+  end
+end