old_contents: from django.db import models
  from rphistory.models import Song
  
  class Track(models.Model):
      track_id = models.CharField(max_length=80)
  
  class TrackMap(models.Model):
      track_id = models.ForeignKey(Track)
      rp_song_id = models.ForeignKey(Song)
      country_code = models.CharField(max_length=2, null=False)
      modified = models.DateTimeField(auto_now=True, auto_now_add=True, null=False)
  
new_contents: from django.db import models
  from rphistory.models import Song
  
  class Track(models.Model):
      spotify_track_id = models.CharField(max_length=80)
  
  class TrackMap(models.Model):
      track = models.ForeignKey(Track)
      rp_song = models.ForeignKey(Song)
      country_code = models.CharField(max_length=2, null=False)
      modified = models.DateTimeField(auto_now=True, auto_now_add=True, null=False)
  
subject: adjust model