lev's routines and handlers have built-in error handling mechanisms (that appropriately interrupt transactions, etc).

so this would mean removing the :status output (since routines shouldn't really be thinking in terms of HTTP status codes) and then replacing line 20 (`app_user.save!`) with:

    app_user.save
    fatal_error(code: :unknown_error_or_whatever) if app_user.errors.any? 

The fatal_error will stop the execution and return to where the top routine/handler was called, in this case https://github.com/Dantemss/accounts/blob/users_index/app/models/user.rb#L69  

There you can change that code to:

    AddUnreadUpdateForUser.call(self).errors.none?