UPnPumpkin plugin API

@pumpkin-plugins/upnpumpkin-api lets one plugin request a leased port mapping from UPnPumpkin through Pumpkin plugin messages. It contains the message protocol, client, watcher, and helper for turning a successful mapping into a public URL.

Watch a mapping

Create a PortMapClient with the plugin message sender, then create a MappingWatcher with a stable key, protocol, internal port, and description. Start the watcher after the plugin loads, call tick() from the plugin's task handler, and call stop() when unloading or when the web service no longer needs the port.

The watcher requests a mapping immediately and refreshes it while running. openUrl returns a URL only when the reported state contains a usable public address. When UPnPumpkin is not installed or has not loaded yet, the watcher reports an unavailable state; callers should handle it without blocking their own service from starting.

Unused requests expire after five minutes. UPnPumpkin also applies a per-plugin mapping limit, so stop watchers promptly. The API package does not perform router discovery itself; the server-side plugin owns that network work.