add comments around usage

Signed-off-by: aramissennyeydd <aramis.sennyey@doordash.com>

.changeset/young-months-admire.md

@@ -1,5 +1,6 @@
 ---
 '@backstage/backend-app-api': minor
+'@backstage/backend-plugin-api': minor
 ---
 
-Adds a new `instanceMetadataService` to hold information about a specific backend instance.
+**EXPERIMENTAL**: Adds a new `instanceMetadataService` to hold information about a specific backend instance.

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

@@ -97,6 +97,7 @@ const instanceRegistry = new (class InstanceRegistry {
   };
 })();
 
+// Duplicating from `@backstage/backend-plugin-api` to avoid a deep import.
 type BackendFeatureMeta =
   | {
       type: 'plugin';
@@ -126,6 +127,7 @@ function createInstanceMetadataServiceFactory(
                 moduleId: feature.moduleId,
               };
             }
+            // Ignore unknown feature types.
             return undefined;
           })
           .filter(Boolean) as BackendFeatureMeta[];

packages/backend/src/instanceMetadata.ts

@@ -18,15 +18,19 @@ import {
   createBackendPlugin,
 } from '@backstage/backend-plugin-api';
 
+// Example usage of the instance metadata service to log the installed features.
 export default createBackendPlugin({
   pluginId: 'instance-metadata-logging',
   register(env) {
     env.registerInit({
       deps: {
         instanceMetadata: coreServices.EXPERIMENTAL_instanceMetadata,
+        logger: coreServices.logger,
       },
-      async init({ instanceMetadata }) {
-        console.log('metadata', instanceMetadata.getInstalledFeatures());
+      async init({ instanceMetadata, logger }) {
+        logger.info(
+          `Installed features on this instance: ${instanceMetadata.getInstalledFeatures()}`,
+        );
       },
     });
   },