Merge with remote

Author: wilburx9

lib/src/models/charge.dart

@@ -1,3 +1,5 @@
+import 'dart:convert';
+
 import 'package:flutter_paystack/src/common/exceptions.dart';
 import 'package:flutter_paystack/src/common/my_strings.dart';
 import 'package:flutter_paystack/src/models/bank.dart';
@@ -81,7 +83,7 @@ class Charge {
  return null;
  }
 
- return _metadata.toString();
+ return jsonEncode(_metadata);
  }
 }