Add OpenSearch store support

Implement OpenSearchStore to support Amazon OpenSearch and open-source
OpenSearch deployments. This addresses the incompatibility with the
Elasticsearch client which rejects OpenSearch servers.

Changes:
- Add OpenSearchStore with async/sync variants
- Implement opensearch-py client integration
- Add sanitization strategies for keys and collections
- Include comprehensive test suite
- Support connection via URL or pre-configured client
- Add optional dependency: opensearch-py[async]>=2.0.0

The implementation mirrors the Elasticsearch store architecture but
uses the opensearch-py client library to avoid product detection errors.

Fixes #209

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: William Easton <[email protected]>

Author: github-actions[bot]

key-value/key-value-aio/pyproject.toml

@@ -40,6 +40,7 @@ valkey = ["valkey-glide>=2.1.0"]
 vault = ["hvac>=2.3.0", "types-hvac>=2.3.0"]
 memcached = ["aiomcache>=0.8.0"]
 elasticsearch = ["elasticsearch>=8.0.0", "aiohttp>=3.12"]
+opensearch = ["opensearch-py[async]>=2.0.0"]
 dynamodb = ["aioboto3>=13.3.0", "types-aiobotocore-dynamodb>=2.16.0"]
 keyring = ["keyring>=25.6.0"]
 keyring-linux = ["keyring>=25.6.0", "dbus-python>=1.4.0"]
@@ -67,7 +68,7 @@ env_files = [".env"]
 
 [dependency-groups]
 dev = [
-    "py-key-value-aio[memory,disk,redis,elasticsearch,memcached,mongodb,vault,dynamodb,rocksdb]",
+    "py-key-value-aio[memory,disk,redis,elasticsearch,opensearch,memcached,mongodb,vault,dynamodb,rocksdb]",
     "py-key-value-aio[valkey]; platform_system != 'Windows'",
     "py-key-value-aio[keyring]",
     "py-key-value-aio[pydantic]",

key-value/key-value-aio/src/key_value/aio/stores/opensearch/__init__.py

@@ -0,0 +1,3 @@
+from key_value.aio.stores.opensearch.store import OpenSearchStore
+
+__all__ = ["OpenSearchStore"]