old_contents: from django.contrib import admin
  from models import Writeboard
  
  class WriteboardAdmin(admin.ModelAdmin):
      prepopulated_fields = {'slug': ('writeboard_name',)}
  
  admin.site.register(Writeboard, WriteboardAdmin)
new_contents: from django.contrib import admin
  from models import Writeboard
  
  admin.site.register(Writeboard,)
subject: simplify admin and remove prepopulated slug