fix wrong import

lexam_api/api/injectors.py

 from injector import Injector
 
 from lexam_api.api.module import LexamAPIModule
+from lexam_api.database.group.module import GroupAccessorModule
 from lexam_api.database.user.module import UserAccessorModule
 
-injector = Injector([LexamAPIModule, UserAccessorModule])
+injector = Injector([LexamAPIModule, UserAccessorModule, GroupAccessorModule])

lexam_api/core/group/port/service/group_service.py

-import datetime
+
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
+from datetime import datetime
 from typing import Optional