Function delete 

pub async fn delete(pool: &PgPool, actor: &Actor, id: Uuid) -> AppResult<String>

Deletes a webhook together with its deliveries.

Invariants

• Permission: administrator (403); unknown webhook is “not found”.
• Locks: the webhook row (FOR UPDATE).
• Data: the deliveries of the webhook are deleted with it.
• Audit: webhook.delete.
• Notifications / webhooks: none.
• Atomic: one transaction.