Add api for optional stock

src/main/java/cn/stock/market/dto/OptionalStockResponse.java

@@ -0,0 +1,18 @@
+package cn.stock.market.dto;
+
+import lombok.Data;
+
+@Data
+public class OptionalStockResponse {
+    private String message;
+    private Integer code;
+    private DataResponse data = new DataResponse();
+
+    @Data
+    public static class DataResponse {
+        private String symbol;
+        private String company;
+        private Double pricecurrent;
+        private Float pricepercentchange;
+    }
+}