from django.contrib.auth import get_user_model
from django.contrib.auth.models import AbstractUser
from django.core.validators import MinValueValidator, MaxValueValidator
from django.db import models


class User(AbstractUser):
    pass


class UserGroup(models.Model):
    name = models.CharField(max_length=100, blank=False, null=False)
    year = models.PositiveIntegerField(blank=False, null=False, validators=[MinValueValidator(1900), MaxValueValidator(2200)])
    is_deleted = models.BooleanField(blank=False, null=False, default=False)
    users = models.ManyToManyField(get_user_model())

    def __str__(self):
        return 'UserGroup {}-{}-{}'.format(self.id, self.name, self.year)