🗃️ Add more cache ability to local database

lib/database/account.dart

@@ -0,0 +1,40 @@
+import 'dart:convert';
+
+import 'package:drift/drift.dart';
+import 'package:surface/types/account.dart';
+
+class SnAccountConverter extends TypeConverter<SnAccount, String>
+    with JsonTypeConverter2<SnAccount, String, Map<String, Object?>> {
+  const SnAccountConverter();
+
+  @override
+  SnAccount fromSql(String fromDb) {
+    return fromJson(jsonDecode(fromDb) as Map<String, dynamic>);
+  }
+
+  @override
+  String toSql(SnAccount value) {
+    return jsonEncode(toJson(value));
+  }
+
+  @override
+  SnAccount fromJson(Map<String, Object?> json) {
+    return SnAccount.fromJson(json);
+  }
+
+  @override
+  Map<String, Object?> toJson(SnAccount value) {
+    return value.toJson();
+  }
+}
+
+@TableIndex(name: 'idx_account_name', columns: {#name})
+class SnLocalAccount extends Table {
+  IntColumn get id => integer().autoIncrement()();
+
+  TextColumn get name => text()();
+
+  TextColumn get content => text().map(const SnAccountConverter())();
+
+  DateTimeColumn get createdAt => dateTime().withDefault(currentDateAndTime)();
+}