Ship orders: shipments with delivery notes

$order->shipments()->create([...]) records a delivery of a paid order's goods on Anikeen ID,
which adds its delivery note to the user's order documents and sends order.shipped.
$shipment->deliveryNote() downloads the PDF.

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

src/Id/Resources/Shipments.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace Anikeen\Id\Resources;
+
+use Anikeen\Id\Concerns\HasBillable;
+use Anikeen\Id\Concerns\HasParent;
+use Throwable;
+
+/**
+ * Deliveries of an order's physical goods. Each one adds a delivery note to the customer's
+ * order documents on Anikeen ID.
+ */
+class Shipments extends BaseCollection
+{
+    use HasBillable;
+    use HasParent;
+
+    /**
+     * Ship goods of a paid order. Only the app that created the order (or a trusted app) can.
+     *
+     * Without `items`, everything physical that hasn't been shipped yet is shipped. Items and
+     * the shipping address are stored as they are now; the user sees them on the delivery note.
+     *
+     * @param array{
+     *     carrier?: string,
+     *     tracking_number?: string,
+     *     tracking_url?: string,
+     *     note?: string,
+     *     shipped_at?: string,
+     *     items?: array<array{order_item_id: string, units?: float|int|string}>
+     * } $attributes
+     *   - carrier:         e.g. "DHL"
+     *   - tracking_url:    http(s) link to track the parcel, shown to the user
+     *   - shipped_at:      when it was sent (default: now, not in the future)
+     *   - items:           physical items of the order and how many of them (default: all left)
+     *
+     * Errors (ResourceException with the HTTP status): 409 when the order isn't paid or nothing
+     * is left to ship, 422 for items that aren't physical items of the order or exceed what's left.
+     *
+     * @throws Throwable
+     */
+    public function create(array $attributes = []): Shipment
+    {
+        return (new Shipment(fn() => $this->billable->anikeenId()
+            ->request('POST', sprintf('v1/orders/%s/shipments', $this->parent->id), $attributes)))
+            ->setBillable($this->billable)
+            ->setParent($this->parent);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function find(string $id): ?Shipment
+    {
+        return (new Shipment(fn() => $this->billable->anikeenId()
+            ->request('GET', sprintf('v1/orders/%s/shipments/%s', $this->parent->id, $id))))
+            ->setBillable($this->billable)
+            ->setParent($this->parent);
+    }
+}