Use DELETE when signing out from registrar area

#599

spec/features/registrar/sign_out_spec.rb

@@ -0,0 +1,15 @@
+require 'rails_helper'
+
+RSpec.feature 'Registrar area sign-out', settings: false do
+  background do
+    Setting.registrar_ip_whitelist_enabled = false
+    sign_in_to_registrar_area(user: create(:api_user_with_unlimited_balance))
+  end
+
+  scenario 'signs the user out' do
+    visit registrar_root_path
+    click_on t('registrar.base.current_user.sign_out')
+
+    expect(page).to have_text('Signed out successfully.')
+  end
+end

spec/requests/registrar/sign_out_spec.rb

@@ -0,0 +1,20 @@
+require 'rails_helper'
+
+RSpec.describe 'Registrar area sign-out', settings: false do
+  describe 'sign-out' do
+    before do
+      sign_in_to_registrar_area
+    end
+
+    it 'signs the user out' do
+      delete registrar_destroy_user_session_path
+      follow_redirect!
+      expect(controller.current_user).to be_nil
+    end
+
+    it 'redirects to login url' do
+      delete registrar_destroy_user_session_path
+      expect(response).to redirect_to(registrar_login_url)
+    end
+  end
+end