old_contents: from django.contrib import admin
  
  from models import Campaign, Referrer
  
  class ReferrerInine(admin.TabularInline):
      model = Referrer
      extra = 0
  
  class CampaignAdmin(admin.ModelAdmin):
      inlines = (ReferrerInine, )
  
  class ReferrerAdmin(admin.ModelAdmin):
      list_display = ('name', 'campaign', 'creation_date')
  
  admin.site.register(Campaign, CampaignAdmin)
  admin.site.register(Referrer, ReferrerAdmin)
  
  
new_contents: from django.contrib import admin
  
  from models import Campaign, Referrer, UserReferrer
  
  class ReferrerInine(admin.TabularInline):
      model = Referrer
      extra = 0
  
  class CampaignAdmin(admin.ModelAdmin):
      inlines = (ReferrerInine, )
  
  class ReferrerAdmin(admin.ModelAdmin):
      list_display = ('name', 'campaign', 'creation_date')
  
  class UserReferrerAdmin(admin.ModelAdmin):
      list_display = ('user', 'referrer')
  
  admin.site.register(Campaign, CampaignAdmin)
  admin.site.register(Referrer, ReferrerAdmin)
  admin.site.register(UserReferrer, UserReferrerAdmin)
  
  
subject: add admin for UserReferrer