Bring the package up to date with the Anikeen ID API

Fixed (called endpoints that don't exist):
- charge(): POST v1/billing/charge (Stripe options aren't passed through anymore)
- Invoice::getInvoiceTemporaryUrl(): GET instead of a non-existent PUT
- OrderItems::create(): POST v1/orders/{order}/items
- createUser() / isEmailExisting(): admin endpoints with the app token
- sshKeysByUserId(): app endpoint; no longer returns the first user's keys for every user
- createOrderPreview(): country_iso goes into billing_address as the API expects
- public endpoints (products, order preview) work without a token
- SshKeys::find() results can be deleted

Added:
- Billable: sshKeys() (create, update, delete), billingOverview(), PaymentMethod::delete()
- AnikeenId: products(), boxes(), shipping labels (list, show, pdf, issue, ship, price list),
  createOrderForUser(), createTransactionForUser(), findOrCreateSocialiteUser()

Requirements: PHP 8.2+, Laravel 11-13 (Laravel 10 and PHP 8.1 are end of life).
Docs generator handles union types; README regenerated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/Id/Concerns/ManagesUserBilling.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace Anikeen\Id\Concerns;
+
+use Anikeen\Id\Result;
+use Throwable;
+
+/**
+ * Orders and payments on behalf of a user. Trusted apps only, sent with the app's token.
+ */
+trait ManagesUserBilling
+{
+    /**
+     * Create an order for a user (VAT from the billing address). With `checkout`, it is paid right
+     * away: with the given `transaction` (a payment captured elsewhere) or by charging the user's
+     * default payment method (402 when declined; the order stays pending and is retried).
+     *
+     * @param string $userId The user's Anikeen ID.
+     * @param array{
+     *     group?: string,
+     *     billing_address_id?: string,
+     *     billing_address?: array,
+     *     shipping_address_id?: string,
+     *     shipping_address?: array,
+     *     items: array<array{type: string, name: string, description?: string, price?: float|string, gross_price?: float|string, unit: string, units: int}>,
+     *     checkout?: bool,
+     *     transaction_id?: string,
+     *     transaction?: array,
+     *     invoice_date?: string,
+     *     currency_iso?: string
+     * } $attributes
+     * @throws Throwable
+     */
+    public function createOrderForUser(string $userId, array $attributes): Result
+    {
+        return $this->asApp()->request('POST', 'v1/admin/orders', [...$attributes, 'user_id' => $userId]);
+    }
+
+    /**
+     * Book a payment of a user that was captured elsewhere (e.g. PayPal, Ko-fi). The same
+     * provider/payment_intent can only be booked once (409 with the existing transaction_id).
+     *
+     * @param string $userId The user's Anikeen ID.
+     * @param array{
+     *     payment_provider?: string,
+     *     payment_intent?: string,
+     *     status: string,
+     *     type: string,
+     *     amount: float|string,
+     *     currency_iso: string,
+     *     created_at: string,
+     *     group?: string,
+     *     invoice_id?: string
+     * } $attributes
+     * @throws Throwable
+     */
+    public function createTransactionForUser(string $userId, array $attributes): Result
+    {
+        return $this->asApp()->request('POST', 'v1/admin/transactions', [...$attributes, 'user_id' => $userId]);
+    }
+}