Add audit log entries for user roles (#19040)

* Refactor audit log schema

* Add audit log entries for user roles

app/models/user_role.rb

@@ -155,6 +155,10 @@ class UserRole < ApplicationRecord
     end
   end
 
+  def to_log_human_identifier
+    name
+  end
+
   private
 
   def in_permissions?(privilege)