Add a `U2fRegistrations` table/model.

- To hold registrations from U2F devices, and to authenticate them.
- Previously, `User#two_factor_enabled` was aliased to the
  `otp_required_for_login` column on `users`.
- This commit changes things a bit:
    - `User#two_factor_enabled` is not a method anymore
    - `User#two_factor_enabled?` checks both the
      `otp_required_for_login` column, as well as `U2fRegistration`s
    - Change all instances of `User#two_factor_enabled` to
      `User#two_factor_enabled?`
- Add the `u2f` gem, and implement registration/authentication at the
  model level.

1 files changed, 13 insertions, 1 deletions

diff --git a/spec/factories/users.rb b/spec/factories/users.rb
index a9b2148bd2a..c6f7869516e 100644
--- a/spec/factories/users.rb
+++ b/spec/factories/users.rb
@@ -15,14 +15,26 @@ FactoryGirl.define do
     end
 
     trait :two_factor do
+      two_factor_via_otp
+    end
+
+    trait :two_factor_via_otp do
       before(:create) do |user|
-        user.two_factor_enabled = true
+        user.otp_required_for_login = true
         user.otp_secret = User.generate_otp_secret(32)
         user.otp_grace_period_started_at = Time.now
         user.generate_otp_backup_codes!
       end
     end
 
+    trait :two_factor_via_u2f do
+      transient { registrations_count 5 }
+
+      after(:create) do |user, evaluator|
+        create_list(:u2f_registration, evaluator.registrations_count, user: user)
+      end
+    end
+
     factory :omniauth_user do
       transient do
         extern_uid '123456'