CAS + SAML authentication feature (#6425)

* Cas authentication feature

* Config

* Remove class_eval + Omniauth initializer

* Codeclimate review

* Codeclimate review 2

* Codeclimate review 3

* Remove uid/email reconciliation

* SAML authentication

* Clean up code

* Improve login form

* Fix code style issues

* Add locales

spec/models/identity_spec.rb

@@ -0,0 +1,5 @@
+require 'rails_helper'
+
+RSpec.describe Identity, type: :model do
+  pending "add some examples to (or delete) #{__FILE__}"
+end