add(IConversationService)：添加会话服务接口

backend/IM_API/Dtos/ClearConversationsDto.cs

@@ -0,0 +1,26 @@
+namespace IM_API.Dtos
+{
+    public class ClearConversationsDto
+    {
+        public int UserId { get; set; }
+        /// <summary>
+        /// 聊天类型
+        /// </summary>
+        public ChatType ChatType { get; set; }
+        /// <summary>
+        /// 目标ID，聊天类型为群则为群id，私聊为用户id
+        /// </summary>
+        public int TargetId { get; set; }
+    }
+    public enum ChatType
+    {
+        /// <summary>
+        /// 私聊
+        /// </summary>
+        single = 0,
+        /// <summary>
+        /// 私聊
+        /// </summary>
+        group = 1
+    }
+}