route to conference#show for custom domain

config/initializers/domain_constraint.rb

@@ -0,0 +1,6 @@
+class DomainConstraint
+  def self.matches?(request)
+  	@domains = Conference.pluck(:custom_domain).compact
+    @domains.include?(request.domain)
+  end
+end

config/routes.rb

@@ -1,5 +1,9 @@
 Osem::Application.routes.draw do
 
+  constraints DomainConstraint do
+    get '/', to: 'conferences#show'
+  end
+
   if ENV['OSEM_ICHAIN_ENABLED'] == 'true'
     devise_for :users, controllers: { registrations: :registrations }
   else