Enable TTL on DynamoDB table creation

This commit adds TTL enablement to the DynamoDB store setup process.
Previously, TTL values were stored in items but the table-level TTL
feature was never enabled, meaning expired items would never be
automatically deleted by DynamoDB.

Changes:
- Added update_time_to_live call in _setup() method
- Enabled TTL on the 'ttl' attribute after table creation
- Added error handling for ValidationException (already enabled case)

This addresses one of the critical issues identified in #168 for
marking DynamoDB store as stable. Batch operations implementation
is deferred to a future PR.

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

Author: github-actions[bot]

key-value/key-value-aio/src/key_value/aio/stores/dynamodb/store.py

@@ -164,6 +164,20 @@ async def _setup(self) -> None:
             waiter = self._connected_client.get_waiter("table_exists")  # pyright: ignore[reportUnknownMemberType, reportUnknownVariableType]
             await waiter.wait(TableName=self._table_name)  # pyright: ignore[reportUnknownMemberType]
 
+        # Enable TTL on the table
+        try:
+            await self._connected_client.update_time_to_live(  # pyright: ignore[reportUnknownMemberType]
+                TableName=self._table_name,
+                TimeToLiveSpecification={
+                    "Enabled": True,
+                    "AttributeName": "ttl",
+                },
+            )
+        except self._connected_client.exceptions.ClientError as e:  # pyright: ignore[reportUnknownMemberType]
+            # TTL may already be enabled, check error code
+            if e.response["Error"]["Code"] != "ValidationException":  # pyright: ignore[reportUnknownMemberType, reportUnknownArgumentType]
+                raise
+
     @override
     async def _get_managed_entry(self, *, key: str, collection: str) -> ManagedEntry | None:
         """Retrieve a managed entry from DynamoDB."""