feat: add database wrapper interfaces for mssql and postgres

Introduce a DB dialect interface and per-dialect wrappers that expose connection, query and column type operations with pre/post SQL hooks.

config.yaml

@@ -10,6 +10,8 @@ defaults:
   batches_per_partition: 8
   truncate_target: true
   truncate_method: TRUNCATE # TRUNCATE | DELETE
+  max_partition_errrors: 5
+  max_chunk_errors: 5
   retry:
     attempts: 3
     base_delay_ms: 500
@@ -26,6 +28,8 @@ jobs:
     target:
       schema: demo
       table: users
+    pre_sql: 
+      - 'SELECT 1'
 
   - name: analytics_events
     enabled: true
@@ -36,3 +40,7 @@ jobs:
     target:
       schema: analytics
       table: events
+    pre_sql: 
+      - 'SELECT 1'
+    post_sql: 
+      - "SELECT 1"