https://docs.djangoproject.com/en/2.1/ref/contrib/admin/#django.contrib.admin.ModelAdmin.readonly_fields
https://www.cnblogs.com/vincenshen/articles/6971835.html
https://www.cnblogs.com/huchong/p/7894660.html
https://code.ziqiangxuetang.com/django/django-admin.html