GRN2-30: Add custom ldap sign in page (#619)

* Add custom ldap signin page

* Remove old omniauth-ldap gem

* Use new bn gems

spec/controllers/users_controller_spec.rb

@@ -387,4 +387,12 @@ describe UsersController, type: :controller do
       expect(response).to redirect_to(root_path)
     end
   end
+
+  context 'GET #ldap_signin' do
+    it "should render the ldap signin page" do
+      get :ldap_signin
+
+      expect(response).to render_template(:ldap_signin)
+    end
+  end
 end