feat(sub): subscription logic (pre release)

schemas/checkout.py

@@ -0,0 +1,15 @@
+from pydantic import BaseModel, Field, computed_field
+
+
+class CheckoutResponse(BaseModel):
+    order_id: str = Field()
+    total_amount: float = Field()
+    bonus_paid: float = Field()
+    amount_to_pay: float = Field()
+
+    payment_link: str | None = Field(None)
+
+    @property
+    @computed_field
+    def is_fully_paid(self):
+        return self.total_amount <= self.bonus_paid and self.amount_to_pay <= 0