refactored HTTP error handling and streamlined UI components by centralizing shared logic and removing redundant parameters

lib/api/mhsl/mhsl_api.dart

@@ -1,21 +1,16 @@
-import 'dart:async';
 import 'dart:convert';
-import 'dart:io';
 
 import 'package:http/http.dart' as http;
-import 'package:jiffy/jiffy.dart';
 
-import '../api_request.dart';
 import '../errors/network_exception.dart';
 import '../errors/parse_exception.dart';
 import '../errors/server_exception.dart';
+import '../http_errors.dart';
 
-abstract class MhslApi<T> extends ApiRequest {
+abstract class MhslApi<T> {
   String subpath;
   MhslApi(this.subpath);
 
-  http.Response? response;
-
   Future<http.Response>? request(Uri uri);
   T assemble(String raw);
 
@@ -24,22 +19,12 @@ abstract class MhslApi<T> extends ApiRequest {
       'https://mhsl.eu/marianum/marianummobile/$subpath',
     );
 
-    final http.Response data;
-    try {
-      final raw = await request(endpoint);
-      if (raw == null) {
-        throw const NetworkException(
-          userMessage: 'Keine Antwort vom MHSL-Dienst erhalten.',
-          technicalDetails: 'mhsl request returned null',
-        );
-      }
-      data = raw;
-    } on SocketException catch (e) {
-      throw NetworkException(technicalDetails: 'mhsl $subpath: ${e.message}');
-    } on TimeoutException catch (e) {
-      throw NetworkException.timeout(technicalDetails: 'mhsl $subpath: $e');
-    } on http.ClientException catch (e) {
-      throw NetworkException(technicalDetails: 'mhsl $subpath: ${e.message}');
+    final data = await sendGuarded('mhsl $subpath', () => request(endpoint));
+    if (data == null) {
+      throw const NetworkException(
+        userMessage: 'Keine Antwort vom MHSL-Dienst erhalten.',
+        technicalDetails: 'mhsl request returned null',
+      );
     }
 
     if (data.statusCode > 299) {
@@ -55,8 +40,4 @@ abstract class MhslApi<T> extends ApiRequest {
       throw ParseException(technicalDetails: 'mhsl $subpath assemble: $e');
     }
   }
-
-  static String dateTimeToJson(DateTime time) =>
-      Jiffy.parseFromDateTime(time).format(pattern: 'yyyy-MM-dd HH:mm:ss');
-  static DateTime dateTimeFromJson(String time) => DateTime.parse(time);
 }