save before flutter upgrade

lib/models/customers/bill_cycle.dart

@@ -0,0 +1,31 @@
+import 'dart:convert';
+
+class BillCycle {
+  BillCycle({
+    required this.customerId,
+    required this.day,
+    required this.billDueDay,
+    required this.graceDays,
+    required this.frequency,
+  });
+
+  int customerId;
+  int day;
+  int billDueDay;
+  int graceDays;
+  int frequency;
+
+  factory BillCycle.fromJson(String str) => BillCycle.fromMap(json.decode(str));
+
+  factory BillCycle.fromMap(Map<String, dynamic> json) {
+    BillCycle billCycle = BillCycle(
+      customerId: json["customer_id"],
+      day: json['day'],
+      billDueDay: json['bill_due_day'],
+      graceDays: json['grace_days'],
+      frequency: json['frequency'],
+    );
+
+    return billCycle;
+  }
+}