commencer: display a FranceConnect button

Fix #3640

app/controllers/users/commencer_controller.rb

@@ -34,6 +34,11 @@ module Users
       redirect_to new_user_registration_path
     end
 
+    def france_connect
+      store_user_location!
+      redirect_to france_connect_particulier_path
+    end
+
     def procedure_for_help
       Procedure.publiees.find_by(path: params[:path]) || Procedure.brouillons.find_by(path: params[:path])
     end

app/views/commencer/show.html.haml

@@ -8,6 +8,7 @@
       %span.optional-on-small-screens
         demarches-simplifiees.fr
     = link_to 'J’ai déjà un compte', commencer_sign_in_path(path: @procedure.path), class: ['button large expand']
+    = render partial: 'shared/france_connect_login', locals: { url: commencer_france_connect_path(path: @procedure.path) }
 
   - else
     - dossiers = current_user.dossiers.where(procedure: @procedure)

config/routes.rb

@@ -270,6 +270,7 @@ Rails.application.routes.draw do
       get '/:path', action: 'commencer'
       get '/:path/sign_in', action: 'sign_in', as: :sign_in
       get '/:path/sign_up', action: 'sign_up', as: :sign_up
+      get '/:path/france_connect', action: 'france_connect', as: :france_connect
     end
 
     resources :dossiers, only: [:index, :show, :new] do

spec/controllers/users/commencer_controller_spec.rb

@@ -112,4 +112,28 @@ describe Users::CommencerController, type: :controller do
       it { expect(subject).to redirect_to(new_user_registration_path) }
     end
   end
+
+  describe '#france_connect' do
+    context 'for a published procedure' do
+      subject { get :france_connect, params: { path: published_procedure.path } }
+
+      it 'set the path to return after sign-up to the procedure start page' do
+        subject
+        expect(controller.stored_location_for(:user)).to eq(commencer_path(path: published_procedure.path))
+      end
+
+      it { expect(subject).to redirect_to(france_connect_particulier_path) }
+    end
+
+    context 'for a draft procedure' do
+      subject { get :france_connect, params: { path: draft_procedure.path } }
+
+      it 'set the path to return after sign-up to the draft procedure start page' do
+        subject
+        expect(controller.stored_location_for(:user)).to eq(commencer_test_path(path: draft_procedure.path))
+      end
+
+      it { expect(subject).to redirect_to(france_connect_particulier_path) }
+    end
+  end
 end

spec/views/commencer/show.html.haml_spec.rb

@@ -21,6 +21,7 @@ RSpec.describe 'commencer/show.html.haml', type: :view do
       subject
       expect(rendered).to have_link('Créer un compte')
       expect(rendered).to have_link('J’ai déjà un compte')
+      expect(rendered).to have_link('S’identifier avec FranceConnect')
     end
   end