use a constant instead of hardcoded value for token validity

src/rest-gateway/app/services/token_service.py

@@ -59,7 +59,7 @@ class TokenService:
 
 
         created_at = datetime.now()
-        valid_until = created_at + timedelta(days=1)
+        valid_until = created_at + timedelta(days=TOKEN_VALIDITY_IN_DAYS)
         return jwt.encode(
             {
                 'username': user.username,