Challenge 3: Convert Manual Lookup to Route Model Binding — Possible Solution
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// BEFORE — manual lookup

use App\Models\Book;

public function show(string $id)
{
    $book = Book::findOrFail($id);
    return view('books.show', ['book' => $book]);
}

// AFTER — route model binding

use App\Models\Book;

public function show(Book $book)
{
    return view('books.show', ['book' => $book]);
}

// routes/web.php — the route parameter name must match the variable name
Route::get('/books/{book}', [BookController::class, 'show'])->name('books.show');

WHAT HAPPENS DIFFERENTLY IF THE ID DOESN'T EXIST
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In BOTH versions, a nonexistent ID actually results in the exact same
outcome: Laravel automatically throws a
Illuminate\Database\Eloquent\ModelNotFoundException, which Laravel's
default exception handling converts into a 404 Not Found response shown
to the visitor.

The difference is entirely about WHERE that behavior comes from:
- In the "before" version, Book::findOrFail($id) is an explicit method
  call the developer wrote — findOrFail() is what throws
  ModelNotFoundException if no row matches; this is visible, deliberate
  code sitting right there in the method body.
- In the "after" version, there is no findOrFail() call anywhere in the
  method at all — Laravel's route model binding does the equivalent
  lookup automatically, BEFORE the show() method's body ever executes,
  and throws the same exception on the framework's own initiative if the
  {book} route segment doesn't correspond to a real Product row.

Practically, this means: if a developer ever needed different behavior
for a missing book (returning a specific fallback book, logging something
custom, redirecting instead of 404ing), route model binding's automatic
behavior would need to be explicitly overridden (e.g. via a custom
resolveRouteBinding() method on the model, or falling back to a manual
$id parameter and calling Book::find($id) instead of Book::findOrFail()) —
whereas with the manual version, that customization is just a normal code
change to the existing findOrFail() call.

WHY THIS WORKS
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- Route model binding matches the {book} segment in the route definition
  to the $book parameter in the controller method BY NAME — this is why
  the route parameter must be named {book} (not {id} or anything else)
  for this specific binding to work automatically.
- The type hint `Book $book` (rather than `string $book`) is what tells
  Laravel which Eloquent model to query — Laravel infers the primary key
  column to look up (id, by default) from the model class itself.