old_contents: from django.db import models
  
  # Create your models here.
  
  class User(models.Model):
  	display_name = models.CharField(max_length=64)
  	auth_key = models.CharField(max_length=64)
  
  class Post(models.Model):
  	user = models.ForeignKey(User)
  	text = models.CharField(max_length=4000)
  
  class Comment(models.Model):
  	user = models.ForeignKey(User)
  	post = models.ForeignKey(Post)
  	text = models.CharField(max_length=4000)
  
new_contents: from django.db import models
  
  # Create your models here.
  
  class User(models.Model):
  	display_name = models.CharField(max_length=64)
  	auth_key = models.CharField(max_length=64)
  
  class Post(models.Model):
  	user = models.ForeignKey(User)
  	text = models.CharField(max_length=4000)
  	last_modified = models.DateTimeField()
  
  class Comment(models.Model):
  	user = models.ForeignKey(User)
  	post = models.ForeignKey(Post)
  	text = models.CharField(max_length=4000)
  
subject: Add 'last modified' field to Post model