Repro for https://github.com/googleapis/nodejs-storage/issues/2389

issue_2389.js

import { Storage } from './build/esm/src/storage.js';
// Path: nodejs-storage/issue_2389.js

const storage = new Storage();
const myBucket = storage.bucket('thebookclub');
const file = myBucket.file('sample.txt');
file.copy('new_sample.txt', {
    contentType: 'outer', // A property from CopyOptions
    metadata: {
        // Typed as FileMetadata
        contentType: 'internal',
        custom1: 'outer', // Not a part of FileMetadata, but allowed by TypeScript
        metadata: {
            // Intended to hold custom metadata, but ignored
            custom2: 'internal',
        },
    },
});
const new_file = myBucket.file('new_sample.txt');
new_file.getMetadata((err, metadata) => {
    console.log(metadata.metadata.custom1); // outer
    console.log(metadata.metadata.custom2); // undefined
});

repro.php

<?php
require __DIR__ . "/vendor/autoload.php";

use Google\Cloud\Storage\StorageClient;

// Create a Storage client
$storage = new StorageClient([
    'projectId' => 'the-book-club-337319',
]);

// Define the bucket name and folder path
$bucketName = 'thebookclub';
$bucket = $storage->bucket($bucketName);
$object = $bucket->object('sample.txt');

$new_object = $object->copy('thebookclub', [
    'name' => 'sample_copy_php.txt',
    'metadata' => [
        'contentType' => 'outer',
        'metadata' => [
            'contentType' => 'internal',
            'custom1' => 'outer',
            'metadata' => [
                'custom2' => 'internal'
            ]
        ],
    ],
]);
print_r($new_object->info());

// php library updates metadata successfully