backend-app-api: export BackendStartupError

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/backend-app-api/report.api.md

@@ -4,6 +4,7 @@
 
 ```ts
 import { BackendFeature } from '@backstage/backend-plugin-api';
+import { CustomErrorBase } from '@backstage/errors';
 import { ServiceFactory } from '@backstage/backend-plugin-api';
 
 // @public (undocumented)
@@ -22,6 +23,15 @@ export interface Backend {
   stop(): Promise<void>;
 }
 
+// @public
+export class BackendStartupError extends CustomErrorBase {
+  constructor(startupResult: BackendStartupResult);
+  // (undocumented)
+  name: 'BackendStartupError';
+  // (undocumented)
+  get result(): BackendStartupResult;
+}
+
 // @public
 export interface BackendStartupResult {
   beginAt: Date;

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

@@ -22,3 +22,4 @@ export type {
   ModuleStartupResult,
 } from './types';
 export { createSpecializedBackend } from './createSpecializedBackend';
+export { BackendStartupError } from './BackendStartupError';