feat: add support for webhooks API

[jayanratna]

This PR adds support for the webhooks API and also adds a verify helper method to the webhooks service.

---

Summary by cubic

Adds full Webhooks API support with CRUD endpoints and request verification, so you can manage webhooks and securely handle incoming events. Bumps SDK version to 0.23.0.

• New Features
  • Webhooks service: get, create, list (limit/before/after), update, remove.
  • verify(payload, headers, secret, tolerance?) to validate Svix-signed requests.
  • Webhook resource with id, status, endpoint, events, signing_secret, created_at.
  • Client exposes $webhooks; service registry and factory updated.
  • Domain resource adds status, capability, and region fields.

[cubic-dev-ai]

2 issues found across 10 files

Prompt for AI agents (all 2 issues)

Understand the root cause of the following 2 issues and fix them.


<file name="src/Webhook.php">

<violation number="1" location="src/Webhook.php:8">
The PHPDoc on $created_at still describes an email instead of the webhook, which makes the new resource documentation misleading. Please update it to describe the webhook timestamp.</violation>
</file>

<file name="src/Service/Webhook.php">

<violation number="1" location="src/Service/Webhook.php:88">
Passing null tolerance into WebhookSignature::verify triggers a TypeError, breaking webhook verification.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[cubic-dev-ai]

Passing null tolerance into WebhookSignature::verify triggers a TypeError, breaking webhook verification.

Prompt for AI agents

Address the following comment on src/Service/Webhook.php at line 88:

<comment>Passing null tolerance into WebhookSignature::verify triggers a TypeError, breaking webhook verification.</comment>

<file context>
@@ -0,0 +1,90 @@
+     */
+    public function verify(string $payload, array $headers, string $secret, ?int $tolerance = null): bool
+    {
+        return WebhookSignature::verify($payload, $headers, $secret, $tolerance);
+    }
+}
</file context>

Suggested change

	return WebhookSignature::verify($payload, $headers, $secret, $tolerance);
	return WebhookSignature::verify($payload, $headers, $secret, $tolerance ?? 300);

[jayanratna]

I have updated the default value from null to 300.