implement FileUploadService and chunked upload models

Models/FileUploadModels.cs

@@ -16,5 +16,20 @@ namespace Chtn.CSharp.SDK.Models.Media
         [JsonProperty("name")] public string Name { get; set; }
         [JsonProperty("fileId")] public string FileId { get; set; }
     }
-    public class RegisterUploadResp { public string UploadId { get; set; } }
+    public class RegisterUploadResp 
+    {
+        [JsonProperty("uploadId")] public string UploadId { get; set; }
+    }
+
+    public class ChunkUploadReq
+    {
+        [JsonProperty("uploadId")] public string UploadId { get; set; }
+        [JsonProperty("chunkIndex")] public int ChunkIndex { get; set; }
+        [JsonProperty("data")] public byte[] Data { get; set; }
+    }
+
+    public class FinishUploadReq
+    {
+        [JsonProperty("uploadId")] public string UploadId { get; set; }
+    }
 }