user_settings - migrate new model

[bllendev]

• [ ] add to admin (inline to User model)

  class UserSettings(models.Model):
  user = models.OneToOneField(
      settings.AUTH_USER_MODEL,
      on_delete=models.CASCADE,
      related_name='settings'
  )
  
  # notifications
  notify_ebook_convert = models.BooleanField(default=True)
  
  # settings
  setting_ebook_convert = models.CharField(default="", blank=True)