fix: resolve currency code correctly for both list and associative-map shapes

[roncodes]

Problem

Two related errors were reported in production:

DEPRECATED  mb_strtolower(): Passing null to parameter #1 ($string) of type string is deprecated
            in vendor/laravel/framework/src/Illuminate/Support/Str.php on line 611.

TypeError: Fleetbase\Support\Utils::getCurrenyFromCountryCode(): Return value must be of type
           ?string, array returned  (Utils.php:1235)

Root cause

The fleetbase/countries package (a fork of PragmaRX Countries) returns the currencies field in two distinct shapes depending on the underlying data source:

Shape	Example	Scope
Sequential list of ISO 4217 strings	["USD"]	Most countries (239)
Associative map — code as key, detail object as value	{"USD": {"name": "United States dollar", "symbol": "$"}}	10 territories: BQ, CC, CX, GP, GF, MQ, YT, RE, SJ, TK

The previous code used Arr::first() unconditionally on the currencies collection:

// Before
'currency' => Arr::first(static::get($country, 'currencies', [])),

• List shape — Arr::first() returns the first element (the code string). ✅
• Map shape — Arr::first() returns the first value (an array like ["name" => "...", "symbol" => "..."]). ❌

This array then propagated into the cached country data and was returned from getCurrenyFromCountryCode(), whose return type is ?string, causing the TypeError.

A secondary issue existed in getCountryCodeByCurrency() which used the dot-notation shorthand currencies.0 (only valid for list-shape countries) and then called strtolower($country['currency']) without a null guard, triggering the mb_strtolower(null) deprecation for map-shape territories.

Fix

Introduce a new Utils::resolveCurrencyCode($currencies): ?string helper that normalises both shapes:

public static function resolveCurrencyCode($currencies): ?string
{
    if (empty($currencies)) {
        return null;
    }

    // Convert Coollection / Collection objects to a plain array.
    if (is_object($currencies) && method_exists($currencies, 'toArray')) {
        $currencies = $currencies->toArray();
    }

    if (!is_array($currencies)) {
        return null;
    }

    // Sequential list shape: ["USD", "EUR", ...]
    if (array_is_list($currencies)) {
        $code = Arr::first($currencies);
        return is_string($code) ? $code : null;
    }

    // Associative map shape: {"USD": {"name": "...", "symbol": "..."}, ...}
    $code = array_key_first($currencies);
    return is_string($code) ? $code : null;
}

Changes

• getCountryData() — replace Arr::first(...currencies...) with resolveCurrencyCode() so the cached country data always stores a string currency code, never an array.
• getCountryCodeByCurrency() — replace currencies.0 dot-notation with resolveCurrencyCode() (fixes map-shape countries), and add an is_string() guard before strtolower() to eliminate the mb_strtolower(null) deprecation.

Affected territories

The following 10 territories had associative-map currencies and were broken before this fix:

cca2	Territory	Currency
BQ	Caribbean Netherlands	USD
CC	Cocos (Keeling) Islands	AUD
CX	Christmas Island	AUD
GP	Guadeloupe	EUR
GF	French Guiana	EUR
MQ	Martinique	EUR
YT	Mayotte	EUR
RE	Réunion	EUR
SJ	Svalbard and Jan Mayen	NOK
TK	Tokelau	NZD