Support third-party checkout confirmation

Orders and subscriptions created by untrusted apps are confirmed by the
user on Anikeen ID. confirmationUrl($returnUrl) on Order and
Subscription builds the link with the return URL; checking out such a
draft throws ConfirmationRequiredException carrying the same URL.

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

src/Id/Concerns/HasConfirmationUrl.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace Anikeen\Id\Concerns;
+
+/**
+ * Orders and subscriptions created by third-party apps are confirmed by the user on Anikeen ID.
+ */
+trait HasConfirmationUrl
+{
+    /**
+     * Where the user confirms (or cancels) this booking, or null once it was checked out.
+     *
+     * Afterwards the user is sent back to $returnUrl with `status` (completed, pending or
+     * cancelled) and `order` or `subscription`. The return URL must have the origin of one of
+     * the app's redirect URIs. Check the status through the API; don't trust the query string.
+     */
+    public function confirmationUrl(?string $returnUrl = null): ?string
+    {
+        $url = $this->confirmation_url ?? null;
+
+        if (!$url || !$returnUrl) {
+            return $url ?: null;
+        }
+
+        return $url . (str_contains($url, '?') ? '&' : '?') . http_build_query(['return_url' => $returnUrl]);
+    }
+}

src/Id/Exceptions/ConfirmationRequiredException.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Anikeen\Id\Exceptions;
+
+use Throwable;
+
+/**
+ * Thrown when a third-party app tries to check out an order or subscription itself: the user has
+ * to confirm it on Anikeen ID. Send them to the confirmation URL instead.
+ */
+class ConfirmationRequiredException extends ResourceException
+{
+    public function __construct(string $message, int $code, public readonly ?string $confirmationUrl = null, ?Throwable $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+}

src/Id/Resources/BaseResource.php

@@ -2,6 +2,7 @@
 
 namespace Anikeen\Id\Resources;
 
+use Anikeen\Id\Exceptions\ConfirmationRequiredException;
 use Anikeen\Id\Exceptions\ResourceException;
 use Anikeen\Id\Result;
 use JsonSerializable;
@@ -19,6 +20,14 @@ abstract class BaseResource implements JsonSerializable
         $this->result = $callable();
 
         if (!$this->result->success()) {
+            if (($this->result->data->error ?? null) === 'confirmation_required') {
+                throw new ConfirmationRequiredException(
+                    $this->result->data->message ?? 'The user has to confirm this on Anikeen ID.',
+                    $this->result->response->getStatusCode(),
+                    $this->result->data->confirmation_url ?? null,
+                );
+            }
+
             throw new ResourceException(sprintf('%s for resource [%s]', rtrim($this->result->data->message, '.'), get_called_class()), $this->result->response->getStatusCode());
         }
 

src/Id/Resources/Order.php

@@ -3,14 +3,17 @@
 namespace Anikeen\Id\Resources;
 
 use Anikeen\Id\Concerns\HasBillable;
+use Anikeen\Id\Concerns\HasConfirmationUrl;
 use Throwable;
 
 /**
  * @property string $id
+ * @property null|string $confirmation_url where the user confirms it (third-party apps)
  */
 class Order extends BaseResource
 {
     use HasBillable;
+    use HasConfirmationUrl;
 
     /**
      * Update given order from the current user.

src/Id/Resources/Subscription.php

@@ -3,6 +3,7 @@
 namespace Anikeen\Id\Resources;
 
 use Anikeen\Id\Concerns\HasBillable;
+use Anikeen\Id\Concerns\HasConfirmationUrl;
 use Anikeen\Id\Contracts\AppTokenRepository;
 use Throwable;
 
@@ -17,10 +18,12 @@ use Throwable;
  * @property string $ends_at
  * @property string $webhook_url
  * @property string $webhook_secret
+ * @property null|string $confirmation_url where the user confirms it (third-party apps)
  */
 class Subscription extends BaseResource
 {
     use HasBillable;
+    use HasConfirmationUrl;
 
     /**
      * Update a given subscription from the current user.