moved to migration strategy, moved daos to top lib

test/drift/sendtrain/generated/schema.dart

@@ -0,0 +1,23 @@
+// dart format width=80
+// GENERATED CODE, DO NOT EDIT BY HAND.
+// ignore_for_file: type=lint
+import 'package:drift/drift.dart';
+import 'package:drift/internal/migrations.dart';
+import 'schema_v1.dart' as v1;
+import 'schema_v2.dart' as v2;
+
+class GeneratedHelper implements SchemaInstantiationHelper {
+  @override
+  GeneratedDatabase databaseForVersion(QueryExecutor db, int version) {
+    switch (version) {
+      case 1:
+        return v1.DatabaseAtV1(db);
+      case 2:
+        return v2.DatabaseAtV2(db);
+      default:
+        throw MissingSchemaException(version, versions);
+    }
+  }
+
+  static const versions = const [1, 2];
+}