cleanup and added unit tests

hartmann-foto-documentation-frontend/lib/pages/customer/customer_widget.dart

@@ -2,6 +2,7 @@ import 'dart:convert' show base64Decode;
 
 import 'package:flutter/material.dart';
 import 'package:fotodocumentation/controller/picture_controller.dart';
+import 'package:fotodocumentation/dto/picture_dto.dart';
 import 'package:fotodocumentation/pages/customer/picture_delete_dialog.dart';
 
 import 'package:go_router/go_router.dart';
@@ -194,6 +195,7 @@ class _CustomerWidgetState extends State<CustomerWidget> {
 
     final dateStr = _dateFormat.format(pictureDto.pictureDate);
     return InkWell(
+      key: Key("table_row_${customerDto.id}"),
       onTap: () => _actionSelect(context, customerDto, pictureDto),
       child: Padding(
         padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
@@ -231,6 +233,7 @@ class _CustomerWidgetState extends State<CustomerWidget> {
             SizedBox(
               width: 48,
               child: IconButton(
+                key: Key("table_row_delete_${customerDto.id}"),
                 icon: Icon(
                   Icons.delete_outline,
                   color: _generalStyle.errorColor,