Retrieve a webhook secret using core API. The webhook secret should be included in the response for the GET and POST methods for the /api/v1/core/webhooks resource.

🔍 Problem Statement

Webhook secrets cannot be retrieved via the Core API. Developers who need to verify webhook signatures must look up the secret in the dashboard manually, which breaks automation and CI/CD provisioning workflows.

💡 User Story

As a developer, I want to retrieve webhook secrets via the Core API, so that I can automate webhook verification setup without manual dashboard lookups.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given a webhook configuration, when a developer calls the API to retrieve it, then the response includes the webhook secret.