Returns the canonical list of event types delivered to partner webhook endpoints — every string is a resource.action pair (e.g. patient.created, customer_invoice.paid, membership.updated). Use this list to type-check incoming webhook payloads against the platform's current event registry. Today there is no per-endpoint subscription filter — once a webhook endpoint is registered (POST /partner/webhook_endpoints), it receives the full set of events the partner's integrations emit. Implementations should ignore unknown event types; new resource/action pairs may be added without a version bump.