registration and login ready, with some validations

apps/mobile/packages/data_connect/lib/src/session/staff_session_store.dart

@@ -0,0 +1,29 @@
+import 'package:krow_domain/krow_domain.dart' as domain;
+
+class StaffSession {
+  final domain.User user;
+  final domain.Staff? staff;
+
+  const StaffSession({
+    required this.user,
+    this.staff,
+  });
+}
+
+class StaffSessionStore {
+  StaffSession? _session;
+
+  StaffSession? get session => _session;
+
+  void setSession(StaffSession session) {
+    _session = session;
+  }
+
+  void clear() {
+    _session = null;
+  }
+
+  static final StaffSessionStore instance = StaffSessionStore._();
+
+  StaffSessionStore._();
+}