frontend-plugin-api: allow duplicate route ref IDs

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

.changeset/witty-pets-march.md

@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-plugin-api': patch
+---
+
+Allow route references to be installed in multiple app instances as long as their name is the same.

packages/frontend-plugin-api/src/routing/RouteRef.test.ts

@@ -35,6 +35,7 @@ describe('RouteRef', () => {
 
     internal.setId('some-id');
     expect(String(internal)).toBe('RouteRef{some-id}');
+    internal.setId('some-id'); // Should allow same ID
 
     expect(() => internal.setId('some-other-id')).toThrow(
       "RouteRef was referenced twice as both 'some-id' and 'some-other-id'",

packages/frontend-plugin-api/src/routing/RouteRef.ts

@@ -95,7 +95,7 @@ export class RouteRefImpl implements InternalRouteRef {
     if (!id) {
       throw new Error(`${this.#name} id must be a non-empty string`);
     }
-    if (this.#id) {
+    if (this.#id && this.#id !== id) {
       throw new Error(
         `${this.#name} was referenced twice as both '${this.#id}' and '${id}'`,
       );