Add model for notifications

- Display a list of active notifications

lib/inventree/notification.dart

@@ -0,0 +1,31 @@
+import "package:inventree/inventree/model.dart";
+
+/*
+ * Class representing a "notification"
+ */
+
+class InvenTreeNotification extends InvenTreeModel {
+
+  InvenTreeNotification() : super();
+
+  InvenTreeNotification.fromJson(Map<String, dynamic> json) : super.fromJson(json);
+
+  @override
+  InvenTreeNotification createFromJson(Map<String, dynamic> json) {
+    return InvenTreeNotification.fromJson(json);
+  }
+
+  @override
+  String get URL => "notifications/";
+
+  String get message => (jsondata["message"] ?? "") as String;
+
+  DateTime? get creationDate {
+    if (jsondata.containsKey("creation")) {
+      return DateTime.tryParse((jsondata["creation"] ?? "") as String);
+    } else {
+      return null;
+    }
+  }
+
+}