test: Add integration tests for loaders and streaming features

New tests:
- test_checkpoint_resume.py - End-to-end resume scenarios
- test_resilient_streaming.py - Resilience with real databases
- Enhanced Snowflake loader tests with state management
- Enhanced PostgreSQL tests with reorg handling
- Updated Redis, DeltaLake, Iceberg, LMDB loader tests

Integration test features:
- Real database containers (PostgreSQL, Redis, Snowflake)
- State persistence and resume testing
- Label joining with actual data
- Reorg detection and invalidation
- Parallel loading with multiple workers
- Error injection and recovery

Tests require Docker for database containers.

Author: fordN

tests/conftest.py

@@ -81,12 +81,14 @@ def snowflake_config():
         'warehouse': os.getenv('SNOWFLAKE_WAREHOUSE', 'test_warehouse'),
         'database': os.getenv('SNOWFLAKE_DATABASE', 'test_database'),
         'schema': os.getenv('SNOWFLAKE_SCHEMA', 'PUBLIC'),
-        'use_stage': True,
+        'loading_method': 'stage',  # Default to stage loading for existing tests
     }
 
     # Add optional parameters if they exist
     if os.getenv('SNOWFLAKE_PASSWORD'):
         config['password'] = os.getenv('SNOWFLAKE_PASSWORD')
+    if os.getenv('SNOWFLAKE_PRIVATE_KEY'):
+        config['private_key'] = os.getenv('SNOWFLAKE_PRIVATE_KEY')
     if os.getenv('SNOWFLAKE_ROLE'):
         config['role'] = os.getenv('SNOWFLAKE_ROLE')
     if os.getenv('SNOWFLAKE_AUTHENTICATOR'):