backend-plugin-api: made defaultFactories internal

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

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

@@ -13,12 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 import {
   ServiceFactory,
   FactoryFunc,
   ServiceRef,
 } from '@backstage/backend-plugin-api';
 
+/**
+ * Keep in sync with `@backstage/backend-plugin-api/src/services/system/types.ts`
+ * @internal
+ */
+export type InternalServiceRef<T> = ServiceRef<T> & {
+  __defaultFactory?: (service: ServiceRef<T>) => Promise<ServiceFactory<T>>;
+};
+
 export class ServiceRegistry {
   readonly #providedFactories: Map<string, ServiceFactory>;
   readonly #loadedDefaultFactories: Map<Function, Promise<ServiceFactory>>;
@@ -38,7 +47,7 @@ export class ServiceRegistry {
 
   get<T>(ref: ServiceRef<T>): FactoryFunc<T> | undefined {
     let factory = this.#providedFactories.get(ref.id);
-    const { defaultFactory } = ref;
+    const { __defaultFactory: defaultFactory } = ref as InternalServiceRef<T>;
     if (!factory && !defaultFactory) {
       return undefined;
     }