old_contents: from django.contrib.auth.models import User
  
  from nightreads.posts.models import Tag
  from .models import UserTag
  
  
  def update_user_tags(user, tags):
      tags_objs = Tag.objects.filter(name__in=tags)
      user.usertag.tags.add(*tags_objs)
      user.save()
  
  
  def get_user(email):
      user, created = User.objects.get_or_create(username=email)
      if created:
          UserTag.objects.create(user=user)
      return user
  
new_contents: from django.contrib.auth.models import User
  
  from nightreads.posts.models import Tag
  from .models import UserTag
  
  
  def update_user_tags(user, tags):
      tags_objs = Tag.objects.filter(name__in=tags)
      if tags_objs:
          user.usertag.tags.clear()
          user.usertag.tags.add(*tags_objs)
      user.save()
  
  
  def get_user(email):
      user, created = User.objects.get_or_create(username=email)
      if created:
          UserTag.objects.create(user=user)
      return user
  
subject: Clear existing tags before updating