old_contents: from django.contrib import admin
  from .models import MaintenanceRecord
  
  # Register your models here.
  admin.site.register(MaintenanceRecord)
  
new_contents: from django.contrib import admin
  from .models import MaintenanceRecord, UserToken, UserPreferences
  
  # Register your models here.
  admin.site.register(MaintenanceRecord)
  admin.site.register(UserToken)
  admin.site.register(UserPreferences)
  
subject: add UserToken and UserPreferences models to /admin