feat: split bills for one deal

models/card_group.py

@@ -25,9 +25,10 @@ class CardGroup(BaseModel):
         back_populates='group',
         secondary='card_relations'
     )
-    bill_request: Mapped[Optional['GroupBillRequest']] = relationship(
+    bill_requests: Mapped[list['GroupBillRequest']] = relationship(
         back_populates='group',
-        lazy='joined'
+        lazy='joined',
+        uselist=True,
     )