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/components/group/chat_group_content.dart

@@ -8,9 +8,26 @@ import '../../blocs/message/message_state.dart';
 import '../../models/group.dart';
 import '../../models/message.dart';
 
+/// Chat group content widget for group messaging functionality.
+/// 
+/// This widget provides a complete chat interface for group members to
+/// communicate within a travel group. Features include:
+/// - Real-time message loading and sending
+/// - Message editing and deletion
+/// - Message reactions (like/unlike)
+/// - Scroll-to-bottom functionality
+/// - Message status indicators
+/// 
+/// The widget integrates with MessageBloc for state management and
+/// handles various message operations through the bloc pattern.
 class ChatGroupContent extends StatefulWidget {
+  /// The group for which to display the chat interface
   final Group group;
 
+  /// Creates a chat group content widget.
+  /// 
+  /// Args:
+  ///   [group]: The group object containing group details and ID
   const ChatGroupContent({
     super.key,
     required this.group,
@@ -21,14 +38,19 @@ class ChatGroupContent extends StatefulWidget {
 }
 
 class _ChatGroupContentState extends State<ChatGroupContent> {
+  /// Controller for the message input field
   final _messageController = TextEditingController();
+  
+  /// Controller for managing scroll position in the message list
   final _scrollController = ScrollController();
+  
+  /// Currently selected message for editing (null if not editing)
   Message? _editingMessage;
 
   @override
   void initState() {
     super.initState();
-    // Charger les messages au démarrage
+    // Load messages when the widget initializes
     context.read<MessageBloc>().add(LoadMessages(widget.group.id));
   }
 
@@ -39,12 +61,20 @@ class _ChatGroupContentState extends State<ChatGroupContent> {
     super.dispose();
   }
 
+  /// Sends a new message or updates an existing message.
+  /// 
+  /// Handles both sending new messages and editing existing ones based
+  /// on the current editing state. Validates input and clears the input
+  /// field after successful submission.
+  /// 
+  /// Args:
+  ///   [currentUser]: The user sending or editing the message
   void _sendMessage(user_state.UserModel currentUser) {
     final messageText = _messageController.text.trim();
     if (messageText.isEmpty) return;
 
     if (_editingMessage != null) {
-      // Mode édition
+      // Edit mode - update existing message
       context.read<MessageBloc>().add(
             UpdateMessage(
               groupId: widget.group.id,
@@ -54,7 +84,7 @@ class _ChatGroupContentState extends State<ChatGroupContent> {
           );
       _cancelEdit();
     } else {
-      // Mode envoi
+      // Send mode - create new message
       context.read<MessageBloc>().add(
             SendMessage(
               groupId: widget.group.id,
@@ -68,6 +98,13 @@ class _ChatGroupContentState extends State<ChatGroupContent> {
     _messageController.clear();
   }
 
+  /// Initiates editing mode for a selected message.
+  /// 
+  /// Sets the message as the currently editing message and populates
+  /// the input field with the message text for modification.
+  /// 
+  /// Args:
+  ///   [message]: The message to edit
   void _editMessage(Message message) {
     setState(() {
       _editingMessage = message;
@@ -75,6 +112,10 @@ class _ChatGroupContentState extends State<ChatGroupContent> {
     });
   }
 
+  /// Cancels the current editing operation.
+  /// 
+  /// Resets the editing state and clears the input field,
+  /// returning to normal message sending mode.
   void _cancelEdit() {
     setState(() {
       _editingMessage = null;
@@ -82,6 +123,13 @@ class _ChatGroupContentState extends State<ChatGroupContent> {
     });
   }
 
+  /// Deletes a message from the group chat.
+  /// 
+  /// Sends a delete event to the MessageBloc to remove the specified
+  /// message from the group's message history.
+  /// 
+  /// Args:
+  ///   [messageId]: The ID of the message to delete
   void _deleteMessage(String messageId) {
     context.read<MessageBloc>().add(
           DeleteMessage(