errors: add explicit name property to ServiceUnavailableError

Every CustomErrorBase subclass explicitly sets `name = 'ClassName' as const`
except ServiceUnavailableError, which relied on the constructor fallback that
reads `this.constructor.name`. This is fragile under minification. Added the
explicit name property for consistency and added a serialization round-trip test.

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

.changeset/add-service-unavailable-error-name.md

@@ -0,0 +1,5 @@
+---
+'@backstage/errors': patch
+---
+
+Added explicit `name` property to `ServiceUnavailableError` for consistency with all other error classes, making it resilient to minification.

packages/errors/report.api.md

@@ -151,7 +151,10 @@ export function serializeError(
 ): SerializedError;
 
 // @public
-export class ServiceUnavailableError extends CustomErrorBase {}
+export class ServiceUnavailableError extends CustomErrorBase {
+  // (undocumented)
+  name: 'ServiceUnavailableError';
+}
 
 // @public
 export function stringifyError(error: unknown): string;

packages/errors/src/errors/common.ts

@@ -100,7 +100,9 @@ export class NotImplementedError extends CustomErrorBase {
  *
  * @public
  */
-export class ServiceUnavailableError extends CustomErrorBase {}
+export class ServiceUnavailableError extends CustomErrorBase {
+  name = 'ServiceUnavailableError' as const;
+}
 
 /**
  * An error that forwards an underlying cause with additional context in the message.

packages/errors/src/serialization/error.test.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { NotModifiedError } from '../errors';
+import { NotModifiedError, ServiceUnavailableError } from '../errors';
 import { deserializeError, serializeError, stringifyError } from './error';
 
 class CustomError extends Error {
@@ -77,6 +77,16 @@ describe('serialization', () => {
     expect(withoutStack2.cause.stack).not.toBeDefined();
   });
 
+  it('round-trips a ServiceUnavailableError', () => {
+    const before = new ServiceUnavailableError('service down');
+    const after = deserializeError(
+      serializeError(before, { includeStack: true }),
+    );
+    expect(after.name).toEqual('ServiceUnavailableError');
+    expect(after.message).toEqual('service down');
+    expect(after.stack).toEqual(before.stack);
+  });
+
   it('stringifies all supported forms', () => {
     expect(stringifyError({})).toEqual("unknown error '[object Object]'");
     expect(