feat: 新增业务字段路径读写工具

新增 TakeBusinessFields、WriteBusinessFields、SetByPath 与 GetByPath 等工具，支持按映射路径写入请求体与解析响应，并更新相关依赖。

service/utils/json_flatten.go

@@ -0,0 +1,43 @@
+package utils
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/tidwall/sjson"
+)
+
+// IsFlatMap 递归判断 map 是否扁平化
+func IsFlatMap(m map[string]interface{}) bool {
+	for _, v := range m {
+		switch val := v.(type) {
+		case map[string]interface{}:
+			return false
+		case []interface{}:
+			for _, item := range val {
+				if _, ok := item.(map[string]interface{}); ok {
+					return false
+				}
+			}
+		}
+	}
+	return true
+}
+
+// UnFlatBySjson 将扁平路径映射还原为嵌套 JSON
+func UnFlatBySjson(flatMap map[string]interface{}) (map[string]interface{}, error) {
+	raw := "{}"
+	for path, val := range flatMap {
+		var err error
+		raw, err = sjson.Set(raw, path, val)
+		if err != nil {
+			return nil, fmt.Errorf("sjson set path %s failed: %w", path, err)
+		}
+	}
+
+	var result map[string]interface{}
+	if err := json.Unmarshal([]byte(raw), &result); err != nil {
+		return nil, fmt.Errorf("parse final json failed: %w", err)
+	}
+	return result, nil
+}