save before flutter upgrade

lib/models/customers/invoice.dart

@@ -0,0 +1,25 @@
+import 'dart:convert';
+
+class Invoice {
+  Invoice({
+    required this.invoiceId,
+    required this.date,
+    required this.code,
+  });
+
+  int invoiceId;
+  DateTime date;
+  String code;
+
+  factory Invoice.fromJson(String str) => Invoice.fromMap(json.decode(str));
+
+  factory Invoice.fromMap(Map<String, dynamic> json) {
+    Invoice invoice = Invoice(
+      invoiceId: json['invoice_id'],
+      date: DateTime.parse(json["created_at"]),
+      code: json['invoice'],
+    );
+
+    return invoice;
+  }
+}