new_contents: from django.contrib.gis import admin
  
  import reversion
  
  from .models import Author, Line, Route
  
  class BaseAuthoredAdmin(reversion.VersionAdmin, admin.ModelAdmin):
      readonly_fields = ('author',)
  
      def save_model(self, request, obj, form, change):
          obj.author = Author.objects.create_from_request(request)
          obj.save()
  
  class LineAdmin(BaseAuthoredAdmin):
      pass
  
  class RouteAdmin(BaseAuthoredAdmin):
      pass
  
  admin.site.register(Line, LineAdmin)
  admin.site.register(Route, RouteAdmin)
  
  
subject: Add admin page