Made GradeAverage persistent

lib/storage/gradeAverages/gradeAveragesSettings.dart

@@ -0,0 +1,15 @@
+
+import 'package:json_annotation/json_annotation.dart';
+
+part 'gradeAveragesSettings.g.dart';
+
+@JsonSerializable()
+class GradeAveragesSettings {
+  bool useGradeSystem;
+  List<int> inputs;
+
+  GradeAveragesSettings({required this.useGradeSystem, required this.inputs});
+
+  factory GradeAveragesSettings.fromJson(Map<String, dynamic> json) => _$GradeAveragesSettingsFromJson(json);
+  Map<String, dynamic> toJson() => _$GradeAveragesSettingsToJson(this);
+}

lib/storage/gradeAverages/gradeAveragesSettings.g.dart

@@ -0,0 +1,21 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'gradeAveragesSettings.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+GradeAveragesSettings _$GradeAveragesSettingsFromJson(
+        Map<String, dynamic> json) =>
+    GradeAveragesSettings(
+      useGradeSystem: json['useGradeSystem'] as bool,
+      inputs: (json['inputs'] as List<dynamic>).map((e) => e as int).toList(),
+    );
+
+Map<String, dynamic> _$GradeAveragesSettingsToJson(
+        GradeAveragesSettings instance) =>
+    <String, dynamic>{
+      'useGradeSystem': instance.useGradeSystem,
+      'inputs': instance.inputs,
+    };