Function register_webhook 

pub fn register_webhook(
    _provider_id: &str,
    config: &Value,
    _tenant: &str,
    _team: Option<&str>,
) -> Option<Value>

Register a webhook for a provider based on its setup answers.

Returns Some(result) with status JSON from declared ops, or None if the provider doesn’t declare webhook ops in its config. The actual webhook registration is handled by the provider’s setup_webhook WASM operation, invoked by the setup engine after this function returns None.