Personal Catalogue: Django & PostgreSQL — Chapter 5, Exercise 1
====================================================

TASK
Build the form, view, template, and label-swapping script from this
chapter, then add one real item of each of the four types through this
new public form.

SOLUTION

1. catalogue/forms.py — the ItemForm ModelForm as given in the chapter,
   with CheckboxSelectMultiple used for the tags widget.

2. catalogue/views.py — ItemCreateView, plus the LABELS dictionary and
   the get_context_data override that builds creator_labels and
   format_labels from it, exactly as shown.

3. catalogue/urls.py — add:

    path('add/', views.ItemCreateView.as_view(), name='item_add'),

4. catalogue/templates/catalogue/item_form.html — extending base.html,
   rendering the two json_script tags, the {% csrf_token %}, and
   {{ form.as_p }}, plus the closing <script> block reading the two
   JSON script tags and wiring up the change listener on the item-type
   select.

5. Visit /add/ four times (or reuse the same page after each
   submission redirects back to the list) and add:

   - A book: title "The Pragmatic Programmer", creator "David Thomas",
     format_detail "paperback", release_year 2019, with the "Author"
     label showing once "book" is selected.
   - A CD: title "Rumours", creator "Fleetwood Mac", format_detail
     "album", release_year 1977, with the "Artist" label showing.
   - A DVD: title "The Matrix", creator "Lana and Lilly Wachowski",
     format_detail "Region 2", release_year 1999, with the "Director"
     label showing.
   - A Blu-ray: title "Blade Runner 2049", creator "Denis Villeneuve",
     format_detail "Region A", release_year 2017, with the "Director"
     label showing.

Confirm all four now appear on the list page from Chapter 4, alongside
whatever was already added through the admin in Chapter 3.

WHY THIS WORKS AS AN ANSWER
----------------------------
It builds every real piece described in the chapter in the correct
files, and exercises all four item types specifically to confirm the
label-swapping behavior genuinely changes per type rather than only
being tested against one.