feat(dev): allow running example app with docker

this PR allows backstage contributors to run the example app against
actual postgres, opensearch and redis services using docker and docker
compose file.

no changeset as this doesn't affect any published packages.

Signed-off-by: Hellgren Heikki <heikki.hellgren@op.fi>

packages/backend/src/index.ts

@@ -15,18 +15,27 @@
  */
 
 import { createBackend } from '@backstage/backend-defaults';
-import { createBackendFeatureLoader } from '@backstage/backend-plugin-api';
+import {
+  coreServices,
+  createBackendFeatureLoader,
+} from '@backstage/backend-plugin-api';
 
 const backend = createBackend();
 
 // An example of how to group together and load multiple features. You can also
 // access root-scoped services by adding `deps`.
 const searchLoader = createBackendFeatureLoader({
-  *loader() {
+  deps: {
+    config: coreServices.rootConfig,
+  },
+  *loader({ config }) {
     yield import('@backstage/plugin-search-backend');
     yield import('@backstage/plugin-search-backend-module-catalog');
     yield import('@backstage/plugin-search-backend-module-explore');
     yield import('@backstage/plugin-search-backend-module-techdocs');
+    if (config.has('search.elasticsearch')) {
+      yield import('@backstage/plugin-search-backend-module-elasticsearch');
+    }
   },
 });