Subscribable

Minimal Subscribable contract used by ServerSideDataSource.getRows when an Observable-based data source is preferred over a Promise. Matches the shape of RxJS Observable and the TC39 Observable proposal — any value that exposes a .subscribe(observer) method returning an unsubscribable handle works without a runtime dependency on RxJS.

The plugin subscribes once, expects exactly one next (the result), and tears the subscription down on complete, error, or when the request is superseded (AbortSignal fires) — which is what causes Angular HttpClient to cancel the underlying XHR.