[Django] カスタムユーザーを利用する

from django.contrib.auth.models import AbstractUser, UnicodeUsernameValidator
from django.db import models
from django.utils.translation import gettext_lazy as _

class User(AbstractUser):

    username_validator = UnicodeUsernameValidator()
    username = models.CharField(
        _('username'),
        max_length=150,
        help_text=_(
            'Required. 150 characters or fewer.'
            ' Letters, digits and @/./+/-/_ only.'),
        validators=[username_validator],
    )
    email = models.EmailField(
        _('email address'),
        unique=True,
        error_messages={
            'unique': _("A user with that email address already exists."),
        },
    )
    EMAIL_FIELD = 'email'
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['username']

    class Meta(AbstractUser.Meta):
        swappable = 'AUTH_USER_MODEL'

from django.contrib.auth.base_user import AbstractBaseUser
from django.contrib.auth.models import PermissionsMixin

class AbstractUser(AbstractBaseUser, PermissionsMixin):
    username_validator = UnicodeUsernameValidator()

    username = models.CharField(
        _('username'),
        max_length=150,
        help_text=_('Required. 150 characters or fewer. Letters, digits and @/./+/-/_ only.'),
        validators=[username_validator],
        error_messages={
            'unique': _("A user with that username already exists."),
        },
        blank=True
    )
    first_name = models.CharField(_('first name'), max_length=30, blank=True)
    last_name = models.CharField(_('last name'), max_length=150, blank=True)
    email = models.EmailField(_('email address'), unique=True)
    is_staff = models.BooleanField(
        _('staff status'),
        default=False,
        help_text=_('Designates whether the user can log into this admin site.'),
    )
    is_active = models.BooleanField(
        _('active'),
        default=True,
        help_text=_(
            'Designates whether this user should be treated as active. '
            'Unselect this instead of deleting accounts.'
        ),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)

    objects = UserManager()

    EMAIL_FIELD = 'email'
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['email']

    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')
        swappable = 'AUTH_USER_MODEL'

    def clean(self):
        super().clean()
        self.email = self.__class__.objects.normalize_email(self.email)

    def get_full_name(self):
        full_name = '%s %s' % (self.first_name, self.last_name)
        return full_name.strip()

    def get_short_name(self):
        return self.first_name

    def email_user(self, subject, message, from_email=None, **kwargs):
        send_mail(subject, message, from_email, [self.email], **kwargs)

from django.contrib.auth.base_user import BaseUserManager

class UserManager(BaseUserManager):
    use_in_migrations = True

    def _create_user(self, username, email, password, **extra_fields):
        if not email:
            raise ValueError('The given email must be set')
        email = self.normalize_email(email)
        username = self.model.normalize_username(username)
        user = self.model(username=username, email=email, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, username, email=None, password=None, **extra_fields):
        extra_fields.setdefault('is_staff', False)
        extra_fields.setdefault('is_superuser', False)
        return self._create_user(username, email, password, **extra_fields)

    def create_superuser(self, username, email=None, password=None, **extra_fields):
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)

        if extra_fields.get('is_staff') is not True:
            raise ValueError('Superuser must have is_staff=True.')
        if extra_fields.get('is_superuser') is not True:
            raise ValueError('Superuser must have is_superuser=True.')

        return self._create_user(username, email, password, **extra_fields)

AUTH_USER_MODEL = 'アプリケーション名.User'