feat: Implement trip invitation functionality and notification handling

- Added TripInvitationRepository for managing trip invitations.
- Created TripInvitation model with serialization methods.
- Implemented notification payload parser for handling FCM notifications.
- Enhanced NotificationService to manage trip invitations and related actions.
- Updated UserRepository to include user search functionality.
- Modified AuthRepository to store multiple FCM tokens.
- Added tests for trip invitation logic and notification payload parsing.
- Updated pubspec.yaml and pubspec.lock for dependency management.

functions/notification_tokens.js

@@ -0,0 +1,27 @@
+/**
+ * Retourne tous les tokens FCM d'un profil utilisateur.
+ *
+ * La méthode supporte le format historique `fcmToken` (string) et le nouveau
+ * format `fcmTokens` (array de strings) pour gérer le multi-appareils.
+ */
+function extractUserFcmTokens(userData) {
+    const tokens = [];
+
+    if (typeof userData.fcmToken === "string" && userData.fcmToken.length > 0) {
+        tokens.push(userData.fcmToken);
+    }
+
+    if (Array.isArray(userData.fcmTokens)) {
+        for (const token of userData.fcmTokens) {
+            if (typeof token === "string" && token.length > 0) {
+                tokens.push(token);
+            }
+        }
+    }
+
+    return tokens;
+}
+
+module.exports = {
+    extractUserFcmTokens,
+};