Implement AuthService and ApiClient core logic

Models/DMServiceModels.cs

@@ -0,0 +1,29 @@
+using Chtn.CSharp.SDK.Models.Common;
+using Newtonsoft.Json;
+using System.Collections.Generic;
+
+namespace Chtn.CSharp.SDK.Models.Chat.DM
+{
+    public class DmMessage
+    {
+        [JsonProperty("msgid")] public string MsgId { get; set; }
+        [JsonProperty("author")] public string Author { get; set; }
+        [JsonProperty("message")] public string Content { get; set; }
+        [JsonProperty("sent_at")] public TimeStamp SentAt { get; set; }
+        [JsonProperty("files")] public List<Attachment> Files { get; set; }
+    }
+
+    public class DmPinMessageReq
+    {
+        [JsonProperty("chatid")] public string ChatId { get; set; }
+        [JsonProperty("messageId")] public string MessageId { get; set; }
+        [JsonProperty("userid")] public string UserId { get; set; }
+    }
+
+    public class DmJoinWsRoomReq
+    {
+        [JsonProperty("connId")] public string ConnId { get; set; }
+        [JsonProperty("chatid")] public string ChatId { get; set; }
+        [JsonProperty("userid")] public string UserId { get; set; }
+    }
+}