API debug exception error only returns filename (not file path) when DOCUMENT_ROOT differs from site folder

[neildaniels]

Describe the bug
In situations where an installation's $_SERVER['DOCUMENT_ROOT'] is set to a secluded folder that is separate from the Kirby installation (and site folder), API exceptions do not return a helpful file path.

To Reproduce
Steps to reproduce the behavior:

1. Set document root to something like /var/www/html/website/public
2. Have a plugin in a folder like /var/www/html/website/site/plugins/example-plugin/index.php
3. Enable debug mode.
4. Do something in a hook that would throw an exception.

Expected behavior
The JSON API error would say a helpful file path where the error occurred. Instead, you only get the filename.

Actual

{
    "status": "error",
    "message": "Kirby\\Cms\\Site::TheStreamable\\ExamplePlugin\\{closure}(): Argument #1 ($foo) must be of type Object, string given",
    "code": 500,
    "exception": "TypeError",
    "key": null,
    "file": "index.php",
    "line": 122,
    "details": [],
    "route": "pages/([a-zA-Z0-9\\.\\-_%= \\+\\@\\(\\)]+)"
}

Expected

{
    "status": "error",
    "message": "Kirby\\Cms\\Site::TheStreamable\\ExamplePlugin\\{closure}(): Argument #1 ($foo) must be of type Object, string given",
    "code": 500,
    "exception": "TypeError",
    "key": null,
    "file": "/var/www/html/website/site/plugins/example-plugin/index.php",
    "line": 122,
    "details": [],
    "route": "pages/([a-zA-Z0-9\\.\\-_%= \\+\\@\\(\\)]+)"
}

(The expected file path could be truly relative, with something like ../site/plugins/example-plugin/index.php, but I don't really care much either way.)

Kirby Version
3.5.3

Additional context
Relavant Kirby line:

kirby/src/Api/Api.php

Line 689 in 38afb2d

'file' => F::relativepath($e->getFile(), $_SERVER['DOCUMENT_ROOT'] ?? null),

It seems that F:: relativepath() handles the scenario that $file is not a descendant of $in by just returning the filename, which seems like an odd choice to me.

kirby/src/Toolkit/F.php

Lines 646 to 661 in 38afb2d

	public static function relativepath(string $file, string $in = null): string
	{
	if (empty($in) === true) {
	return basename($file);
	}
	// windows
	$file = str_replace('\\', '/', $file);
	$in = str_replace('\\', '/', $in);
	if (Str::contains($file, $in) === false) {
	return basename($file);
	}
	return Str::after($file, $in);
	}

[lukasbestle]

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