add currency object

Frontend/lib/mih_components/mih_objects/currency.dart

@@ -0,0 +1,23 @@
+class Currency {
+  final String code;
+  final String name;
+
+  const Currency({
+    required this.code,
+    required this.name,
+  });
+
+  factory Currency.fromJson(Map<String, dynamic> json) {
+    return switch (json) {
+      {
+        "code": String code,
+        'name': String name,
+      } =>
+        Currency(
+          code: code,
+          name: name,
+        ),
+      _ => throw const FormatException('Failed to load Currency object.'),
+    };
+  }
+}