Filtering unseen messages in Python Django

Question

I have two models, ChatBox and Message. I want to loop through all chats and display them, and I want to display a count of unseen messages (Message model is in a foreign key relation) for each chat.

Could anyone please help me to do this since I ve been strugling with it for few hours.

Firstly I wanted to pass each object from the loop to django filters/tags and add a count of unseen messages to it, but I got advised to use objects.annotation. However, i can not find ways to implement none of these.

Here is my view that displays inbox:

class InboxView(LoginRequiredMixin, ListView):
  model = ChatBox
  template_name = 'chat/inbox.html'

  def get_queryset(self):
    # getting all chats for a request.user
    object_list = ChatBox.objects.filter(Q(user1=self.request.user) \
    | Q(user2=self.request.user)).all()
    return object_list

And here are my models:

class ChatBox(models.Model):
    user1  = models.ForeignKey(CustomUser, 
    on_delete=models.CASCADE, related_name='user1')
    user2  = models.ForeignKey(CustomUser, 
    on_delete=models.CASCADE, related_name='user2')
    slug = models.SlugField(_("Slug"), max_length=255, unique=True)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)

class Message(models.Model):
  chat = models.ForeignKey(ChatBox, on_delete=models.CASCADE)
  sender = models.ForeignKey(CustomUser, on_delete=models.CASCADE, related_name='sender')
  body = models.TextField()
  created = models.DateTimeField(auto_now_add=True)
  updated = models.DateTimeField(auto_now=True)
  seen = models.BooleanField(default=False)