fix: fix order_by on search API (#62)

Sources/AliyunpanSDK/AliyunpanScope/File/SearchFile.swift

@@ -24,7 +24,7 @@ extension AliyunpanFileScope {
             /// 查询语句，样例：固定目录搜索，只搜索一级 parent_file_id = '123' 精确查询 name = '123' 模糊匹配 name match '123' 搜索指定后缀文件 file_extension = 'apk'  范围查询 created_at < '2019-01-14T00:00:00' 复合查询： type = 'folder' or name = '123' parent_file_id = 'root' and name = '123' and category = 'video'
             public let query: String?
             /// created_at ASC | DESC updated_at ASC | DESC name ASC | DESC size ASC | DESC
-            public let order_by: OrderBy?
+            public let order_by: String?
             /// 生成的视频缩略图截帧时间，单位ms，默认120000ms
             public let video_thumbnail_time: Int?
             /// 生成的视频缩略图宽度，默认480px
@@ -34,16 +34,20 @@ extension AliyunpanFileScope {
             /// 是否返回总数
             public let return_total_count: Bool?
 
-            public init(drive_id: String, limit: Int?, marker: String?, query: String?, order_by: OrderBy?, video_thumbnail_time: Int?, video_thumbnail_width: Int?, image_thumbnail_width: Int?, return_total_count: Bool?) {
+            public init(drive_id: String, limit: Int?, marker: String?, query: String?, order_by: OrderBy?, order_direction: OrderDirection?, video_thumbnail_time: Int?, video_thumbnail_width: Int?, image_thumbnail_width: Int?, return_total_count: Bool?) {
                 self.drive_id = drive_id
                 self.limit = limit
                 self.marker = marker
                 self.query = query
-                self.order_by = order_by
                 self.video_thumbnail_time = video_thumbnail_time
                 self.video_thumbnail_width = video_thumbnail_width
                 self.image_thumbnail_width = image_thumbnail_width
                 self.return_total_count = return_total_count
+                if let order_by = order_by, let order_direction = order_direction {
+                    self.order_by = "\(order_by) \(order_direction)"
+                } else {
+                    self.order_by = nil
+                }
             }
         }