old_contents: from app import db
  
  class User(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      nick = db.Column(db.String(14), unique=True)
      user_phone = db.Column(db.String(20), unique=True)
      user_did = db.Column(db.String(), unique=True)
      is_subbed = db.Column(db.Boolean, default=False)
  
      def __init__(self, nick, user_phone, user_did):
          self.nick = nick
          self.user_phone = user_phone
          self.user_did = user_did
  
new_contents: from app import db
  
  class User(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      nick = db.Column(db.String(14), unique=True)
      user_phone = db.Column(db.String(20), unique=True)
      user_did = db.Relationship('DID', backref='user', lazy='dynamic')
      is_subbed = db.Column(db.Boolean, default=True)
      is_admin = db.Column(db.Boolean, default=False)
  
      def __init__(self, nick, user_phone, user_did):
          self.nick = nick
          self.user_phone = user_phone
          self.user_did = user_did
  
  
  class DID(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      number = db.Column(db.String(20), unique=True)
      user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=True)
       
      def __init__(self, number):
          self.number = number
  
subject: Update database models for prebought DIDs