old_contents: import os
  import datetime
  
  from django.db import models
  
  from abacus_edu.behaviors import Timestampable
  
  
  def set_filename_format(filename):
      now = datetime.datetime.now()
      return "{filename}-{date}-{microsecond}{extension}".format(
          filename=filename,
          date=now.date().strftime("%Y-%m-%d"),
          microsecond=now.microsecond,
          extension=os.path.splitext(filename)[1],
      )
  
  
  def get_representative_image_path(instance, filename):
      now = datetime.datetime.now()
      path = "representative_image/{app_name}/{filename}".format(
          app_name=instance.app_name,
          filename=set_filename_format(filename),
      )
      return path
  
  
  class Application(Timestampable, models.Model):
      app_name = models.CharField(
          max_length=30,
          verbose_name="어플리케이션 이름",
          unique=True,
      )
      slug = models.SlugField(
          max_length=30,
          verbose_name="Slug (URL로 사용됨)",
          unique=True,
      )
      representative_image = models.ImageField(
          upload_to=get_representative_image_path,
          blank=True,
          verbose_name="대표 이미지 (유튜브 영상이 링크가 안 될때 보여주는 이미지)",
      )
  
      def __str__(self):
          return self.app_name
  
      class Meta:
          verbose_name = "Application"
          verbose_name_plural = "Application"
  
new_contents: import os
  import datetime
  
  from django.db import models
  
  from abacus_edu.behaviors import Timestampable
  
  
  def set_filename_format(filename):
      now = datetime.datetime.now()
      return "{filename}-{date}-{microsecond}{extension}".format(
          filename=filename,
          date=now.date().strftime("%Y-%m-%d"),
          microsecond=now.microsecond,
          extension=os.path.splitext(filename)[1],
      )
  
  
  def get_representative_image_path(instance, filename):
      now = datetime.datetime.now()
      path = "representative_image/{app_name}/{filename}".format(
          app_name=instance.app_name,
          filename=set_filename_format(filename),
      )
      return path
  
  
  class Application(Timestampable, models.Model):
      app_name = models.CharField(
          max_length=30,
          verbose_name="어플리케이션 이름",
          unique=True,
      )
      slug = models.SlugField(
          max_length=30,
          verbose_name="Slug (URL로 사용됨)",
          unique=True,
      )
      representative_image = models.ImageField(
          upload_to=get_representative_image_path,
          blank=True,
          verbose_name="대표 이미지 (유튜브 영상이 링크가 안 될때 보여주는 이미지)",
      )
      description = models.TextField(blank=True)
  
      def __str__(self):
          return self.app_name
  
      class Meta:
          verbose_name = "Application"
          verbose_name_plural = "Application"
  
subject: add description field in Application model