Challenge 1: Write a Background Task — Possible Solution
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# catalog/tasks.py

from celery import shared_task

@shared_task
def generate_book_report(book_id):
    from .models import Book
    book = Book.objects.get(pk=book_id)  # re-fetched fresh inside the task
    print(f"Report: '{book.title}' — ${book.price}, in_stock={book.in_stock}")

# catalog/views.py

from django.shortcuts import get_object_or_404, redirect
from .models import Book
from .tasks import generate_book_report

def request_book_report(request, book_id):
    book = get_object_or_404(Book, pk=book_id)
    generate_book_report.delay(book.pk)  # pass the ID, not `book` itself
    return redirect("book-detail", book_id=book.pk)

WHY THIS WORKS
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- generate_book_report(book_id) accepts a plain integer (or whatever type
  the primary key is) rather than a Book instance — integers serialize to
  JSON trivially when Celery sends the task message to the broker, unlike
  a full Django model instance.
- The task re-fetches the book with Book.objects.get(pk=book_id) INSIDE
  the task body, at the moment the worker actually runs it — this
  guarantees the data reflects the book's current state at execution
  time, not whatever it looked like back when .delay() was called in the
  view.
- The view calls generate_book_report.delay(book.pk) — passing book.pk
  (just the ID) rather than book itself — and returns a redirect
  immediately without waiting for the task to actually run; the report
  generation happens later, on a separate worker process, completely
  decoupled from this request/response cycle.