add proper docs

Signed-off-by: Kiss Miklos <miklos@roadie.io>

.changeset/calm-files-hunt.md

@@ -2,4 +2,4 @@
 '@backstage/plugin-search-backend-module-elasticsearch': patch
 ---
 
-Allow indexPrefix configuration through the app-config.yaml
+Allow `indexPrefix` configuration through the `app-config.yaml`

docs/features/search/search-engines.md

@@ -238,3 +238,20 @@ search:
 ```
 
 > You can also increase the batch size if you are using a large ES instance.
+
+### Elasticsearch Index Name Customization
+
+By default, the Elasticsearch indexer creates index names based on their type, a separator, and the current date as a postfix. You can configure a custom prefix for all indices by adding the following section to your app configuration.
+
+An example of a default index name would look like this:  
+`software-catalog-index__20250219`
+
+To prefix all indices with a custom string (e.g., `custom-prefix`), use the following configuration:
+
+```yaml
+search:
+  elasticsearch:
+    indexPrefix: custom-prefix-
+```
+
+After applying this setting, an index name would look like this: `custom-prefix-software-catalog-index__20250219`

plugins/search-backend-module-elasticsearch/src/engines/ElasticSearchSearchEngineIndexer.ts

@@ -140,7 +140,7 @@ export class ElasticSearchSearchEngineIndexer extends BatchSearchEngineIndexer {
     // does not occur, and clean up the empty index we just created.
     if (this.processed === 0) {
       this.logger.warn(
-        `Index for ${this.indexName} was not ${
+        `Index for ${this.indexName} of ${this.type} was not ${
           this.removableIndices.length ? 'replaced' : 'created'
         }: indexer received 0 documents`,
       );
@@ -158,9 +158,9 @@ export class ElasticSearchSearchEngineIndexer extends BatchSearchEngineIndexer {
     // stale indices can be referenced for deletion in case initial attempt
     // fails. Allow errors to bubble up so that we can clean up the created index.
     this.logger.info(
-      `Indexing completed for index ${this.indexName} in ${duration(
-        this.startTimestamp,
-      )}`,
+      `Indexing completed for index ${this.indexName} of ${
+        this.type
+      } in ${duration(this.startTimestamp)}`,
       result,
     );
     await this.elasticSearchClientWrapper.updateAliases({