api-ref: move opaque helper to frontend-internal

Share the internal ApiRef opaque helper through frontend-internal and fail fast when ApiRef-shaped values have an unsupported opaque version.

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

packages/frontend-plugin-api/src/apis/system/ApiRef.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { OpaqueType } from '@internal/opaque';
+import { OpaqueApiRef } from '@internal/frontend';
 import type { ApiRef } from './types';
 
 /**
@@ -31,20 +31,6 @@ type ApiRefBuilderConfig<TId extends string> = {
   pluginId?: string;
 };
 
-/** @internal */
-export const OpaqueApiRef = OpaqueType.create<{
-  public: ApiRef<unknown> & {
-    readonly $$type: '@backstage/ApiRef';
-  };
-  versions: {
-    readonly version: 'v1';
-    readonly pluginId?: string;
-  };
-}>({
-  type: '@backstage/ApiRef',
-  versions: ['v1'],
-});
-
 function validateId(id: string): void {
   const valid = id
     .split('.')