lowercase document type for OpenSearch index campatibility (#7899)

Signed-off-by: hk-9 <pvharikrishna8120@gmail.com>

Author: HK-9

workspaces/confluence/.changeset/many-eggs-lick.md

@@ -0,0 +1,5 @@
+---
+'@backstage-community/plugin-search-backend-module-confluence-collator': patch
+---
+
+Lowercase the document type passed to the collator factory to prevent OpenSearch invalid_index_name_exception in multi-instance configurations

workspaces/confluence/plugins/search-backend-module-confluence-collator/src/module.ts

@@ -102,7 +102,7 @@ export const searchModuleConfluenceCollator = createBackendModule({
               config,
               { logger },
               actualInstanceKey,
-              collatorKey,
+              collatorKey.toLowerCase(),
             ),
           });
         }