Sign in with a user linked by france connect sub (openid)

instead of looking linked user by email because :

- follows FC recommendation to fetch ds account by openid
- the email is not a valid key as many user can share the same FCI email.

The following scenario is now working

A user A (email: 1@mail.com) uses FC to connect to DS
=> It is connected as 1@mail.com

Another user B (email: generic@mail.com) uses FC to connect
=> It is connected as generic@mail.com

The first user A change its FC email to generic@mail.com and connect to DS
=> It is still connected as 1@mail.com

spec/models/france_connect_information_spec.rb

@@ -18,15 +18,5 @@ describe FranceConnectInformation, type: :model do
         expect(fci.user.email).to eq(fci.email_france_connect)
       end
     end
-
-    context 'when a user with same email (but who is not an instructeur) exist' do
-      let(:user) { create(:user) }
-      let(:fci) { build(:france_connect_information, email_france_connect: user.email) }
-      let(:subject) { fci.associate_user! }
-
-      before { subject }
-
-      it { expect(fci.user).to eq(user) }
-    end
   end
 end