old_contents: from django.core.validators import RegexValidator
  from django.db import models
  
  
  class Person(models.Model):
      salutation = models.CharField("Anrede", max_length=50, null=False, blank=False)
      title = models.CharField("Titel", max_length=50, null=True)
      first_name = models.CharField('Vorname', max_length=50, null=False, blank=False)
      last_name = models.CharField('Nachname', max_length=50, null=False, blank=False)
      nickname = models.CharField('Fahrtenname', max_length=50, blank=False, null=True)
      birthdate = models.DateField("Geburtstag", null=True)
      date_of_death = models.DateField("Todestag", null=True)
  
      def common_name(self):
          return f"{self.first_name} {self.last_name}"
  
      def postal_name(self):
          return f"{self.salutation} {self.first_name} {self.last_name}"
  
      def __str__(self):
          if self.nickname:
              return f"{self.first_name} '{self.nickname}' {self.last_name}"
          else:
              return self.common_name()
  
      class Meta:
          verbose_name = 'Person'
          verbose_name_plural = 'Personen'
  
  
  class Adress(models.Model):
      person = models.ForeignKey(Person, null=False)
      street = models.CharField("Straßenname", max_length=100)
      zip = models.CharField("PLZ", max_length=10)
      town = models.CharField("Stadt", max_length=50)
  
  
  class PhoneNumber(models.Model):
      person = models.ForeignKey(Person, null=False)
      label = models.CharField("Bezeichner", max_length=100)
      phone_regex = RegexValidator(regex=r'^\d+$')
      number = models.CharField(validators=[phone_regex], max_length=20)
  
new_contents: from django.core.validators import RegexValidator
  from django.db import models
  
  
  class Person(models.Model):
      salutation = models.CharField("Anrede", max_length=50, null=False, blank=False)
      title = models.CharField("Titel", max_length=50, null=True)
      first_name = models.CharField('Vorname', max_length=50, null=False, blank=False)
      last_name = models.CharField('Nachname', max_length=50, null=False, blank=False)
      nickname = models.CharField('Fahrtenname', max_length=50, blank=False, null=True)
      birthdate = models.DateField("Geburtstag", null=True)
      date_of_death = models.DateField("Todestag", null=True)
      email = models.EmailField("Email", null=True)
  
      def common_name(self):
          return f"{self.first_name} {self.last_name}"
  
      def postal_name(self):
          return f"{self.salutation} {self.first_name} {self.last_name}"
  
      def __str__(self):
          if self.nickname:
              return f"{self.first_name} '{self.nickname}' {self.last_name}"
          else:
              return self.common_name()
  
      class Meta:
          verbose_name = 'Person'
          verbose_name_plural = 'Personen'
  
  
  class Adress(models.Model):
      person = models.ForeignKey(Person, null=False)
      street = models.CharField("Straßenname", max_length=100)
      zip = models.CharField("PLZ", max_length=10)
      town = models.CharField("Stadt", max_length=50)
  
  
  class PhoneNumber(models.Model):
      person = models.ForeignKey(Person, null=False)
      label = models.CharField("Bezeichner", max_length=100)
      phone_regex = RegexValidator(regex=r'^\d+$')
      number = models.CharField(validators=[phone_regex], max_length=20)
  
subject: Add email field to Person