Bug description When performing a similarity search with SearchRequest, the index name is not included. This leads to a permission error when using roles restricted to specific indices in Opensearch.

Contents - Fixed the issue where the index name was missing in similaritySearch. The index was included for adding and deleting documents but not for search. I added it to ensure correct behavior.

Test - Added tests to verify documents are correctly added and retrieved. - Tested this with different indices using separate OpenSearchVectorStore instances.

Issue Link close #885

Comment From: markpollack

Thanks, much appreciated!! Merged in 5431bdd956e60fba4b9f5d04d0498eb35212b058