refactored DomainConstraint and conference_controller_spec

use params id instead of OSEM_HOSTNAME to load conference

config/initializers/domain_constraint.rb

@@ -1,6 +1,6 @@
 class DomainConstraint
   def self.matches?(request)
-  	@domains = Conference.pluck(:custom_domain).compact
-    @domains.include?(request.domain)
+    domains = Conference.where.not(custom_domain: nil).pluck(:custom_domain)
+    domains.include?(request.domain)
   end
-end
+end