Implement mail service with configuration and settings management

FoodsharingSiegen.Server/config/appsettings.example.json

@@ -0,0 +1,26 @@
+{
+  "Kestrel": {
+    "Endpoints": {
+      "Http": {
+        "Url": "http://+:56000"
+      }
+    }
+  },
+  "DetailedErrors": true,
+  "Settings": {
+    "TestMode": true,
+    "Mail": {
+      "Host": "mail.example.com",
+      "Port": 587,
+      "Username": "your_username",
+      "Password": "your_password",
+      "FromAddress": "no-reply@example.com",
+      "UseSsl": true
+    },
+    "Terms": {
+      "Title": "Foodsharing Musterhausen",
+      "TitleShort": "Musterhausen",
+      "StepInName": "Neulingstreffen"
+    }
+  }
+}