old_contents: from django.db import models
  from django.contrib.auth.models import User
  
  class Survey(models.Model):
      created = models.DateTimeField()
      survey_id = models.CharField(max_length=200, unique=True)
      description = models.TextField()
      definition = models.TextField()
  
  class History(models.Model):
      user = models.ForeignKey(User)
      date = models.DateTimeField(auto_now_add=True)
      survey = models.ForeignKey(Survey)
      epidb_id = models.CharField(max_length=36, null=True)
  
  class Profile(models.Model):
      user = models.ForeignKey(User, unique=True)
      last_survey = models.ForeignKey(History)
      last_survey_date = models.DateTimeField()
  
  class Unsaved(models.Model):
      history = models.ForeignKey(History)
      date = models.DateTimeField()
      data = models.TextField()
  
new_contents: from django.db import models
  from django.contrib.auth.models import User
  
  class Survey(models.Model):
      created = models.DateTimeField()
      survey_id = models.CharField(max_length=200, unique=True)
      description = models.TextField()
      definition = models.TextField()
  
  class History(models.Model):
      user = models.ForeignKey(User)
      date = models.DateTimeField(auto_now_add=True)
      survey = models.ForeignKey(Survey)
      epidb_id = models.CharField(max_length=36, null=True)
  
  class Info(models.Model):
      user = models.ForeignKey(User, unique=True)
      last_survey = models.ForeignKey(History)
      last_survey_date = models.DateTimeField()
  
  class Unsaved(models.Model):
      history = models.ForeignKey(History)
      date = models.DateTimeField()
      data = models.TextField()
  
subject: Change model name.