Remember what store the user selected last (#595)

Feedback: several people scanned several times for the wrong store
because the default one was always the same.

Now we put in the storage the ID of the last store selected by the user,
so that when s/he comes back on MyECL during an event on behalf of one
club, the virtual money goes the right store.

Author: Marc-Andrieu

lib/paiement/providers/selected_store_provider.dart

@@ -1,25 +1,50 @@
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:titan/paiement/class/user_store.dart';
 import 'package:titan/paiement/providers/my_stores_provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 class SelectedStoreNotifier extends StateNotifier<UserStore> {
   SelectedStoreNotifier(super.store);
 
   void updateStore(UserStore store) {
     state = store;
+    SharedPreferences.getInstance().then((pref) {
+      pref.setString('selectedStoreId', store.id);
+    });
+  }
+}
+
+class LoadSelectedStoreIdProvider extends StateNotifier<String?> {
+  LoadSelectedStoreIdProvider() : super(null);
+
+  void loadSelectedStoreId() {
+    SharedPreferences.getInstance().then((pref) {
+      state = pref.getString('selectedStoreId');
+    });
   }
 }
 
+final loadSelectedStoreIdProvider =
+    StateNotifierProvider<LoadSelectedStoreIdProvider, String?>((ref) {
+      LoadSelectedStoreIdProvider loadSelectedStoreIdProvider =
+          LoadSelectedStoreIdProvider();
+      loadSelectedStoreIdProvider.loadSelectedStoreId();
+      return loadSelectedStoreIdProvider;
+    });
+
 final selectedStoreProvider =
     StateNotifierProvider<SelectedStoreNotifier, UserStore>((ref) {
       final myStores = ref.watch(myStoresProvider);
+      final selectedStoreId = ref.watch(loadSelectedStoreIdProvider);
       final store = myStores.maybeWhen<UserStore>(
         orElse: () => UserStore.empty(),
         data: (value) {
-          if (value.isEmpty) {
-            return UserStore.empty();
-          }
-          return value.first;
+          if (value.isEmpty) return UserStore.empty();
+          if (selectedStoreId == null) return value.first;
+          return value.firstWhere(
+            (store) => store.id == selectedStoreId,
+            orElse: () => value.first,
+          );
         },
       );
       return SelectedStoreNotifier(store);