Refactor Api-Client

Add Exceptionhandler, AlertService JSON-Converter
AppSettings via DI

Reformat Code

Jugenddienst Stunden/Interfaces/IAlertService.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Jugenddienst_Stunden.Interfaces; 
+internal interface IAlertService {
+	event EventHandler<string> AlertRaised;
+	void Raise(string message);
+}