Added api for sending feedback

lib/api/mhsl/server/feedback/addFeedback.dart

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+import 'dart:convert';
+
+import 'package:http/http.dart';
+import 'package:marianum_mobile/api/mhsl/mhslApi.dart';
+import 'package:http/http.dart' as http;
+
+import 'addFeedbackParams.dart';
+
+
+class AddFeedback extends MhslApi<void> {
+  AddFeedbackParams params;
+  AddFeedback(this.params) : super('server/feedback');
+
+  @override
+  void assemble(String raw) {}
+
+  @override
+  Future<Response>? request(Uri uri) {
+    return http.post(uri, body: jsonEncode(params.toJson()));
+  }
+}

lib/api/mhsl/server/feedback/addFeedbackParams.dart

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+import 'package:json_annotation/json_annotation.dart';
+
+part 'addFeedbackParams.g.dart';
+
+@JsonSerializable()
+class AddFeedbackParams {
+  String user;
+  String feedback;
+  int appVersion;
+
+
+  AddFeedbackParams({
+    required this.user,
+    required this.feedback,
+    required this.appVersion,
+  });
+
+  factory AddFeedbackParams.fromJson(Map<String, dynamic> json) => _$AddFeedbackParamsFromJson(json);
+  Map<String, dynamic> toJson() => _$AddFeedbackParamsToJson(this);
+}

lib/api/mhsl/server/feedback/addFeedbackParams.g.dart

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+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'addFeedbackParams.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+AddFeedbackParams _$AddFeedbackParamsFromJson(Map<String, dynamic> json) =>
+    AddFeedbackParams(
+      user: json['user'] as String,
+      feedback: json['feedback'] as String,
+      appVersion: json['appVersion'] as int,
+    );
+
+Map<String, dynamic> _$AddFeedbackParamsToJson(AddFeedbackParams instance) =>
+    <String, dynamic>{
+      'user': instance.user,
+      'feedback': instance.feedback,
+      'appVersion': instance.appVersion,
+    };