added guardian login with views for their assigned childs

test/push/direct_push_registration_test.dart

@@ -0,0 +1,46 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/push/direct_push_registration.dart';
+import 'package:marianum_mobile/push/push_secure_storage.dart';
+
+class _MemoryStorage implements FlutterSecureStorageLike {
+  final Map<String, String> values = {};
+
+  @override
+  Future<String?> read({required String key}) async => values[key];
+
+  @override
+  Future<void> write({required String key, required String? value}) async {
+    if (value == null) {
+      values.remove(key);
+    } else {
+      values[key] = value;
+    }
+  }
+
+  @override
+  Future<void> delete({required String key}) async => values.remove(key);
+}
+
+void main() {
+  test('device identifier is generated once and then reused', () async {
+    final storage = _MemoryStorage();
+    final registration = DirectPushRegistration(storage: storage);
+    final first = await registration.deviceIdentifier();
+    expect(first, matches(RegExp(r'^[0-9a-f]{32}$')));
+    expect(await registration.deviceIdentifier(), first);
+    expect(
+      await DirectPushRegistration(storage: storage).deviceIdentifier(),
+      first,
+    );
+  });
+
+  test('separate installs get different identifiers', () async {
+    final a = await DirectPushRegistration(
+      storage: _MemoryStorage(),
+    ).deviceIdentifier();
+    final b = await DirectPushRegistration(
+      storage: _MemoryStorage(),
+    ).deviceIdentifier();
+    expect(a, isNot(b));
+  });
+}