old_contents: from django.contrib import admin
  from .models import Card, FaqQuestion, Banner, Rule
  
  admin.site.register(Card)
  admin.site.register(FaqQuestion)
  admin.site.register(Rule)
  admin.site.register(Banner)
  
new_contents: from django.contrib import admin
  from django.contrib.admin import EmptyFieldListFilter
  from django.contrib.auth.admin import UserAdmin
  from django.contrib.auth.models import User
  
  from .models import Card, FaqQuestion, Banner, Rule
  
  
  class WatchlistFilter(EmptyFieldListFilter):
      def __init__(self, field, request, params, model, model_admin, field_path):
          super().__init__(field, request, params, model, model_admin, field_path)
          self.title = "vaktliste"
  
      def choices(self, changelist):
          for lookup, title in (
              (None, 'Alle'),
              ('1', 'På vaktliste'),
              ('0', 'Ikke på vaktliste'),
          ):
              yield {
                  'selected': self.lookup_val == lookup,
                  'query_string': changelist.get_query_string({self.lookup_kwarg: lookup}),
                  'display': title,
              }
  
  
  class CustomUserAdmin(UserAdmin):
      list_filter = UserAdmin.list_filter + (("watches", WatchlistFilter),)
  
  
  admin.site.unregister(User)
  admin.site.register(User, CustomUserAdmin)
  admin.site.register(Card)
  admin.site.register(FaqQuestion)
  admin.site.register(Rule)
  admin.site.register(Banner)
  
subject: Add filter for users on watchlist