feat(sub): handling upgrade/downgrade

rw integration and /me endpoints are left

db/models/invoice.py

@@ -7,7 +7,7 @@ from db.base import Base
 from schemas.invoices import InvoiceStatus
 
 if TYPE_CHECKING:
-    from db.models import User
+    from db.models import Order, User
 
 
 class Invoice(Base):
@@ -17,9 +17,11 @@ class Invoice(Base):
         INTEGER, autoincrement=True, unique=True, nullable=False, primary_key=True
     )
     creator_id: Mapped[int] = mapped_column(ForeignKey("users.id"), nullable=False)
+    order_id: Mapped[int | None] = mapped_column(ForeignKey("orders.id"), nullable=True)
     amount: Mapped[float] = mapped_column(FLOAT, nullable=False)
     status: Mapped[InvoiceStatus] = mapped_column(
         Enum(InvoiceStatus, name="invoicestatus"), nullable=False, default=InvoiceStatus.ACTIVE
     )
 
     creator: Mapped["User"] = relationship("User", lazy="selectin")
+    order: Mapped["Order | None"] = relationship("Order", lazy="selectin")