Add audit log entries for user roles (#19040)

* Refactor audit log schema

* Add audit log entries for user roles

app/models/user.rb

@@ -181,6 +181,14 @@ class User < ApplicationRecord
     update!(disabled: false)
   end
 
+  def to_log_human_identifier
+    account.acct
+  end
+
+  def to_log_route_param
+    account_id
+  end
+
   def confirm
     new_user      = !confirmed?
     self.approved = true if open_registrations? && !sign_up_from_ip_requires_approval?