Webhook configuration for receiving asynchronous task updates.
Wire fields: url (required), id (client-assigned, supports multiple
callbacks per task), token (opaque per-task validation token),
authentication (optional auth info).
Summary
Types
@type t() :: %A2aEngine.Types.PushNotificationConfig{ authentication: A2aEngine.Types.PushNotificationAuthenticationInfo.t() | nil, id: String.t() | nil, token: String.t() | nil, url: String.t() }