refactored DomainConstraint and conference_controller_spec

use params id instead of OSEM_HOSTNAME to load conference

spec/controllers/conferences_controller_spec.rb

@@ -23,12 +23,17 @@ describe ConferencesController do
         get :show, id: conference.short_title
         expect(response).to render_template :show
       end
+    end
 
-      it 'assigns correct conference from a custom domain' do
+    context 'accessing conference via custom domain' do
+      before do
         conference.update_attribute(:custom_domain, 'lvh.me')
         @request.host = 'lvh.me'
+      end
 
+      it 'assigns correct conference' do
         get :show
+
         expect(response).to render_template :show
         expect(assigns(:conference)).to eq conference
       end