old_contents: from django.contrib import admin
  from django.contrib.sites.models import Site
  
  from .models import Church
  
  admin.site.site_header = "Churches of Bridlington Administration"
  
  admin.site.register(Church)
  admin.site.unregister(Site)
  
new_contents: from django.contrib import admin
  from django.contrib.sites.models import Site
  
  from .models import Church
  
  admin.site.site_header = "Churches of Bridlington Administration"
  
  admin.site.register(Church)
  
subject: Undo deregistration of Site object