你好，我有一个遗留数据库，其中包含一个用户表，我想只是添加到这个表的一些字段和覆盖Django模型的抽象基本用户身份验证的问题是，当我试图迁移是说，表用户已经存在于数据库中

from django.contrib.auth.base_user import AbstractBaseUser,BaseUserManager
from django.db import models
import sha512_crypt
import time

# function that return actual timestamp
def actual_epoch_time():
    return int(time.time())
class UserManager(BaseUserManager):
    def create_user(self,email,username,password=None):
        user = self.model(email = normalize_email(email),username=username)
        user.set_password(password)
        user.save()
        return user
    def create_superuser(self,email,username,password=None):
        user = self.create_user(username=username,password=password,email=email)
        user.is_admin = True
        user.save()
        return user

#here is the abstracted user model from xui database with additional fields
class Users(AbstractBaseUser):
    username = models.CharField(max_length=50, blank=True, null=True,unique=True)
    password = models.CharField(max_length=255, blank=True, null=True)
    email = models.CharField(max_length=255, blank=True, null=True)
    ip = models.CharField(max_length=255, blank=True, null=True)
    date_registered = models.IntegerField(default=actual_epoch_time())
    last_login = models.IntegerField(blank=True, null=True)
    member_group_id = models.IntegerField(blank=True, null=True)
    credits = models.FloatField(blank=True, null=True)
    notes = models.TextField(blank=True, null=True)
    status = models.IntegerField(blank=True, null=True)
    reseller_dns = models.TextField(blank=True, null=True)
    owner_id = models.IntegerField(blank=True, null=True)
    override_packages = models.TextField(blank=True, null=True)
    hue = models.CharField(max_length=50, blank=True, null=True)
    theme = models.IntegerField(blank=True, null=True)
    timezone = models.CharField(max_length=255, blank=True, null=True)
    api_key = models.CharField(max_length=64, blank=True, null=True)
 

    objects = UserManager()

    USERNAME_FIELD = 'username'
    class Meta:
        managed = True
        db_table = 'users'

    def set_password(self, raw_password):
        self.password = sha512_crypt.encrypt(raw_password,rounds=200000)
    def check_password(self, raw_password):
        return sha512_crypt.verify(raw_password,self.password)

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