Enhance model and service documentation with detailed comments and descriptions

- Updated Group, Trip, User, and other model classes to include comprehensive documentation for better understanding and maintainability.
- Improved error handling and logging in services, including AuthService, ErrorService, and StorageService.
- Added validation and business logic explanations in ExpenseService and TripService.
- Refactored method comments to follow a consistent format across the codebase.
- Translated error messages and comments from French to English for consistency.

lib/blocs/user/user_event.dart

@@ -1,24 +1,47 @@
+/// Abstract base class for all user-related events.
+/// 
+/// All user events in the application should inherit from this class.
+/// This provides a common interface for user-related operations.
 abstract class UserEvent {}
 
+/// Event to initialize the current user's data.
+/// 
+/// This event is typically dispatched when the app starts or when
+/// a user signs in to load their profile information from Firestore.
 class UserInitialized extends UserEvent {}
 
-class UserLoaded extends UserEvent {
+/// Event to load a specific user's data by their ID.
+/// 
+/// This event is used to fetch user information from Firestore
+/// when you need to display or work with a specific user's data.
+class LoadUser extends UserEvent {
+  /// The ID of the user to load.
   final String userId;
   
-  UserLoaded(this.userId);
+  /// Creates a [LoadUser] event with the specified [userId].
+  LoadUser(this.userId);
 }
 
+/// Event to update the current user's data.
+/// 
+/// This event is dispatched when the user modifies their profile
+/// information and the changes need to be saved to Firestore.
 class UserUpdated extends UserEvent {
+  /// Map containing the user data fields to update.
+  /// 
+  /// Only the fields present in this map will be updated in Firestore.
+  /// This allows for partial updates of user information.
   final Map<String, dynamic> userData;
   
+  /// Creates a [UserUpdated] event with the specified [userData].
   UserUpdated(this.userData);
 }
 
+/// Event to handle user logout.
+/// 
+/// This event is dispatched when the user signs out of the application,
+/// clearing their data from the user bloc state.
 class UserLoggedOut extends UserEvent {
+  /// Creates a [UserLoggedOut] event.
   UserLoggedOut();
 }
-class LoadUser extends UserEvent {
-  final String userId;
-  
-  LoadUser(this.userId);
-}