feat:新增接口

schemas/purchase.py

@@ -0,0 +1,24 @@
+"""申购相关 DTO。"""
+from decimal import Decimal
+
+from pydantic import BaseModel, Field, field_serializer
+
+from schemas.holdings import HoldingResp
+
+
+class PurchaseReq(BaseModel):
+    """申购入参。amount 为正数（元），按净值折算份额。"""
+
+    product_id: int
+    amount: Decimal = Field(gt=0)
+
+
+class PurchaseResp(BaseModel):
+    """申购结果：最新余额 + 该产品最新持仓。"""
+
+    balance: Decimal
+    holding: HoldingResp
+
+    @field_serializer("balance")
+    def _fmt_balance(self, value: Decimal) -> str:
+        return f"{value:.2f}"