api-ref: keep plugin ownership metadata internal

Hide plugin ownership metadata from the public ApiRef type while preserving internal ownership resolution for the builder-based API ref flow.

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

packages/frontend-app-api/src/wiring/createSpecializedApp.test.tsx

@@ -168,6 +168,7 @@ describe('createSpecializedApp', () => {
               "factory": {
                 "api": {
                   "$$type": "@backstage/ApiRef",
+                  "T": null,
                   "id": "core.featureflags",
                   "pluginId": "app",
                   "toString": [Function],
@@ -182,6 +183,7 @@ describe('createSpecializedApp', () => {
               "factory": {
                 "api": {
                   "$$type": "@backstage/ApiRef",
+                  "T": null,
                   "id": "core.app-tree",
                   "pluginId": "app",
                   "toString": [Function],
@@ -196,6 +198,7 @@ describe('createSpecializedApp', () => {
               "factory": {
                 "api": {
                   "$$type": "@backstage/ApiRef",
+                  "T": null,
                   "id": "core.config",
                   "pluginId": "app",
                   "toString": [Function],
@@ -210,6 +213,7 @@ describe('createSpecializedApp', () => {
               "factory": {
                 "api": {
                   "$$type": "@backstage/ApiRef",
+                  "T": null,
                   "id": "core.route-resolution",
                   "pluginId": "app",
                   "toString": [Function],
@@ -224,6 +228,7 @@ describe('createSpecializedApp', () => {
               "factory": {
                 "api": {
                   "$$type": "@backstage/ApiRef",
+                  "T": null,
                   "id": "core.identity",
                   "pluginId": "app",
                   "toString": [Function],

packages/frontend-app-api/src/wiring/createSpecializedApp.tsx

@@ -455,9 +455,10 @@ function createApiFactories(options: {
 
 // TODO(Rugvip): It would be good if this was more explicit, but I think that
 //               might need to wait for some future update for API factories.
-function getApiOwnerId(apiRef: { id: string; pluginId?: string }): string {
-  if (apiRef.pluginId) {
-    return apiRef.pluginId;
+function getApiOwnerId(apiRef: { id: string }): string {
+  const pluginId = (apiRef as { pluginId?: string }).pluginId;
+  if (pluginId) {
+    return pluginId;
   }
 
   const apiRefId = apiRef.id;