fix: Resolve dependency issue with sql stores

Author: kthota-g

src/a2a/server/tasks/__init__.py

@@ -1,9 +1,10 @@
 """Components for managing tasks within the A2A server."""
 
+import logging
+
 from a2a.server.tasks.base_push_notification_sender import (
     BasePushNotificationSender,
 )
-from a2a.server.tasks.database_task_store import DatabaseTaskStore
 from a2a.server.tasks.inmemory_push_notification_config_store import (
     InMemoryPushNotificationConfigStore,
 )
@@ -18,6 +19,18 @@
 from a2a.server.tasks.task_updater import TaskUpdater
 
 
+log = logging.getLogger(__name__)
+
+try:
+    from a2a.server.tasks.database_task_store import DatabaseTaskStore
+except ImportError as e:
+    # If the database task store is not available, we can still use in-memory stores.
+    log.debug(
+        'DatabaseTaskStore not loaded. This is expected if database dependencies are not installed. Error: %s',
+        e,
+    )
+    DatabaseTaskStore = None
+
 __all__ = [
     'BasePushNotificationSender',
     'DatabaseTaskStore',