refactor(auth): Improve exception messages

- Use string interpolation
- Use const constructors

Author: fulleni

lib/src/services/jwt_auth_token_service.dart

@@ -1,4 +1,4 @@
-import 'dart:convert'; // For potential base64 decoding if needed
+// For potential base64 decoding if needed
 
 import 'package:dart_jsonwebtoken/dart_jsonwebtoken.dart';
 import 'package:ht_api/src/services/auth_token_service.dart';
@@ -103,7 +103,7 @@ class JwtAuthTokenService implements AuthTokenService {
       final jti = jwt.payload['jti'] as String?;
       if (jti == null || jti.isEmpty) {
         print(
-            '[validateToken] Token validation failed: Missing or empty "jti" claim.');
+            '[validateToken] Token validation failed: Missing or empty "jti" claim.',);
         // Throw specific exception for malformed token
         throw const BadRequestException(
           'Malformed token: Missing or empty JWT ID (jti) claim.',
@@ -114,7 +114,7 @@ class JwtAuthTokenService implements AuthTokenService {
       final isBlacklisted = await _blacklistService.isBlacklisted(jti);
       if (isBlacklisted) {
         print(
-            '[validateToken] Token validation failed: Token is blacklisted (jti: $jti).');
+            '[validateToken] Token validation failed: Token is blacklisted (jti: $jti).',);
         // Throw specific exception for blacklisted token
         throw const UnauthorizedException('Token has been invalidated.');
       }

lib/src/services/token_blacklist_service.dart

@@ -1,7 +1,7 @@
 import 'dart:async';
 
-import 'package:meta/meta.dart';
 import 'package:ht_shared/ht_shared.dart'; // Added for OperationFailedException
+import 'package:meta/meta.dart';
 
 /// {@template token_blacklist_service}
 /// Defines the interface for a service that manages a blacklist of
@@ -68,7 +68,7 @@ class InMemoryTokenBlacklistService implements TokenBlacklistService {
     );
   }
 
-  // Stores jti -> expiry DateTime
+  /// Stores jti -> expiry DateTime
   @visibleForTesting
   final Map<String, DateTime> blacklistStore = {};
   Timer? _cleanupTimer;
@@ -95,7 +95,7 @@ class InMemoryTokenBlacklistService implements TokenBlacklistService {
         '[InMemoryTokenBlacklistService] Error adding jti $jti to store: $e',
       );
       throw OperationFailedException(
-        'Failed to add token to blacklist: ${e.toString()}',
+        'Failed to add token to blacklist: $e',
       );
     }
   }
@@ -128,7 +128,7 @@ class InMemoryTokenBlacklistService implements TokenBlacklistService {
         '[InMemoryTokenBlacklistService] Error checking blacklist for jti $jti: $e',
       );
       throw OperationFailedException(
-        'Failed to check token blacklist: ${e.toString()}',
+        'Failed to check token blacklist: $e',
       );
     }
   }