chore: minor fixes and formatting

db/models/invoices.py

@@ -1,8 +1,9 @@
 from datetime import datetime
 from enum import Enum as E_cls
-from sqlalchemy import DateTime, func, Enum
-from sqlalchemy.orm import Mapped, mapped_column
+
+from sqlalchemy import DateTime, Enum, func
 from sqlalchemy.dialects.postgresql import BIGINT
+from sqlalchemy.orm import Mapped, mapped_column
 
 from db.base import Base