feat(account invitation): accomplish sign up before accepting the invitation

app/controllers/accept_account_invitations_controller.rb

@@ -4,8 +4,15 @@ class AcceptAccountInvitationsController < ApplicationController
   def show
     return if user_signed_in?
 
-    session[:after_sign_in_url] = request.fullpath
-    redirect_to new_user_session_url(email: AccountInvitation.find_by!(token: ps.fetch(:token)).email)
+    session[:after_authentication_url] = request.fullpath
+
+    invitee_email = AccountInvitation.find_by!(token: ps[:token]).email
+    user = User.find_by(email: invitee_email)
+    if user.present?
+      redirect_to new_user_session_url(email: invitee_email)
+    else
+      redirect_to new_user_registration_url(email: invitee_email)
+    end
   end
 
   def update
@@ -16,6 +23,6 @@ def update
   private
 
   helper_method memoize def received_invitation
-    AccountInvitation.unaccepted.for(current_user).find_by!(token: ps.fetch(:token))
+    AccountInvitation.unaccepted.for(current_user).find_by!(token: ps[:token])
   end
 end

app/controllers/users/registrations_controller.rb

@@ -1,4 +1,12 @@
 class Users::RegistrationsController < Devise::RegistrationsController
+  def new
+    if params.key?(:email)
+      self.resource = User.new(email: params[:email])
+    else
+      super
+    end
+  end
+
   def create
     super do |user|
       user.create_account(name: user.email, email: user.email) if user.persisted?
@@ -10,4 +18,13 @@ def create
   def devise_mapping
     @devise_mapping ||= Devise.mappings[:user]
   end
+
+  private
+
+  def after_sign_up_path_for(resource)
+    after_authentication_url = session.delete(:after_authentication_url)
+    return after_authentication_url if after_authentication_url.present?
+
+    super
+  end
 end

app/controllers/users/sessions_controller.rb

@@ -13,8 +13,8 @@ def new
     private
 
     def after_sign_in_path_for(_resource)
-      after_sign_in_url = session.delete(:after_sign_in_url)
-      return after_sign_in_url if after_sign_in_url.present?
+      after_authentication_url = session.delete(:after_authentication_url)
+      return after_authentication_url if after_authentication_url.present?
 
       super
     end

spec/controllers/accept_account_invitations_spec.rb

@@ -6,7 +6,7 @@
   describe '#show' do
     let(:account) { create(:account, :parent) }
     let(:user) { create(:user, account: account) }
-    let(:second_user) { create(:user, account: account) }
+    let(:second_user) { create(:user) }
 
     let!(:account_invitation) { create(:account_invitation, user: user, account: account, email: second_user.email) }
 
@@ -21,6 +21,15 @@
       end
     end
 
+    context 'when the user not signed up' do
+      let(:account_invitation) { create(:account_invitation, user: user, account: account) }
+
+      it 'redirects to registration url with email' do
+        subject
+        expect(response).to redirect_to(new_user_registration_url(email: account_invitation.email))
+      end
+    end
+
     context 'when the user signed in' do
       before { sign_in second_user }