Function load_documents_by_ids 

pub async fn load_documents_by_ids(
    document_ids: &[String],
) -> Result<Vec<Document>>

Load multiple documents by their IDs

This function efficiently loads multiple documents using their IDs. It uses tokio::task::JoinSet to load documents concurrently, which significantly improves performance when loading many documents from slower storage backends. Returns a vector of successfully loaded documents.