backend-app-api: add methods accepts a backend feature factory

Signed-off-by: Vincenzo Scamporlino <vincenzos@spotify.com>

packages/backend-app-api/src/wiring/BackstageBackend.ts

@@ -28,8 +28,8 @@ export class BackstageBackend implements Backend {
     this.#initializer = new BackendInitializer(this.#services);
   }
 
-  add(feature: BackendFeature): void {
-    this.#initializer.add(feature);
+  add(feature: BackendFeature | (() => BackendFeature)): void {
+    this.#initializer.add(typeof feature === 'function' ? feature() : feature);
   }
 
   async start(): Promise<void> {

packages/backend-app-api/src/wiring/types.ts

@@ -26,7 +26,7 @@ import {
  * @public
  */
 export interface Backend {
-  add(feature: BackendFeature): void;
+  add(feature: BackendFeature | (() => BackendFeature)): void;
   start(): Promise<void>;
   stop(): Promise<void>;
 }