estendendo o modelo de usuário existente

# models.py
class User(AbstractUser):
    username = None
    email = models.EmailField(unique=True, verbose_name=_("email"))
    phone = models.CharField(unique=True, max_length=11, verbose_name=_("phone"))
    ...
    USERNAME_FIELD = "email"
    EMAIL_FIELD = "email"
    ...

class Employee(models.Model):
    ...
    user = models.OneToOneField(
        "user.User",
        on_delete=models.CASCADE,
        related_name="employee",
        verbose_name=_("user"),
    )

class Company(models.Model):
    ...

class Member(models.Model):
    is_owner = models.BooleanField(default=False, verbose_name=_("owner"))
    is_manager = models.BooleanField(default=False, verbose_name=_("manager"))
    is_active = models.BooleanField(default=True)
    user = models.OneToOneField(
        "user.User",
        on_delete=models.CASCADE,
        related_name="member",
        verbose_name=_("user"),
    )
    company = models.ForeignKey(
        "user.Company",
        on_delete=models.CASCADE,
        related_name="members",
        verbose_name=_("company"),
    )
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