old_contents: from django.conf import settings
  from django.contrib.auth import get_user_model
  
  from celery import Task
  
  from users.utils.send_email import send_email
  
  
  class SendWriteDiaryEmailTask(Task):
  
      def run(self):
          for user in get_user_model().objects.all():
              send_email(
                  sender=settings.ADMIN_SENDER_EMAIL,
                  receiver=user.email,
                  subject=settings.WRITE_DIARY_EMAIL_SUBJECT.format(
                      username=user.username,
                  ),
                  text=settings.WRITE_DIARY_EMAIL_TEXT.format(
                      username=user.username,
                  )
              )
  
new_contents: from django.conf import settings
  from django.contrib.auth import get_user_model
  from datetime import datetime
  
  from celery import Task
  
  from users.utils.send_email import send_email
  
  
  class SendWriteDiaryEmailTask(Task):
  
      def run(self):
          today = datetime.now().strftime("%Y/%m/%d")
          for user in get_user_model().objects.all():
              if not user.diary_set.get_or_none(datetime=today):
                  send_email(
                      sender=settings.ADMIN_SENDER_EMAIL,
                      receiver=user.email,
                      subject=settings.WRITE_DIARY_EMAIL_SUBJECT.format(
                          username=user.username,
                      ),
                      text=settings.WRITE_DIARY_EMAIL_TEXT.format(
                          username=user.username,
                      )
                  )
  
subject: update SendWriteDiaryEmailTask: send email to users who didn't write diary