[update]: model class methods

app/models/account.py

@@ -22,6 +22,15 @@ class Account(db.Model):
     #     viewonly=True
     # )
 
+    @classmethod
+    def is_valid_account(cls, account_id, customer_id):
+        account = cls.query.filter_by(id=account_id, customer_id=customer_id).first()
+        if not account:
+            return False, "Account not found or doesn't belong to customer"
+        if account.lien_amount > 0:
+            return False, "Account has an existing lien"
+        return True, "Account is valid"
+
     def __repr__(self):
         return f'<Account {self.id}>'