add deleted_at base table.

Author: hpoul

lib/src/tables/base_tables.dart

@@ -15,6 +15,8 @@ abstract class TableConstants {
 
   final columnCreatedAt = 'created_at';
 
+  final columnDeletedAt = 'deleted_at';
+
   String get typeTimestampNotNull => '$typeTimestamp NOT NULL';
 
   String get specColumnCreatedAt => '$columnCreatedAt $typeTimestampNotNull '