API routes file (routes/api.php)

api.php

<?php

use App\Http\Controllers\GetBookByIsbnController;
use App\Http\Controllers\GetBooksController;
use Illuminate\Support\Facades\Route;

Route::get('/books', GetBooksController::class);
Route::get('/books/{isbn}', GetBookByIsbnController::class)->where('isbn', '[0-9]{10,13}');