add(conversation):完善私聊好友会话服务

backend/IM_API/Domain/Events/DomainEvent.cs

@@ -0,0 +1,13 @@
+using IM_API.Domain.Interfaces;
+
+namespace IM_API.Domain.Events
+{
+    public abstract record DomainEvent: IEvent
+    {
+        public Guid EventId { get; init; } = Guid.NewGuid();
+        public DateTime OccurredAt { get; init; } = DateTime.UtcNow;
+        public long OperatorId { get; init; }
+        public string AggregateId { get; init; } = "";
+        public abstract string EventType { get; }
+    }
+}

backend/IM_API/Domain/Events/MessageCreatedEvent.cs

@@ -0,0 +1,22 @@
+using IM_API.Dtos;
+using IM_API.Models;
+
+namespace IM_API.Domain.Events
+{
+    public record MessageCreatedEvent : DomainEvent
+    {
+        public override string EventType => "IM.MESSAGE.MESSAGE_CREATED";
+        public ChatType ChatType { get; set; }
+        public MessageMsgType MessageMsgType { get; set; }
+        public int MessageId { get; set; }
+        public string MessageContent { get; set; }
+        public int MsgSenderId { get; set; }
+        public int MsgRecipientId { get; set; }
+        public MessageState State { get; set; }
+        public DateTime MessageCreated { get; set; }
+        public string StreamKey { get; set; }
+
+
+
+    }
+}

backend/IM_API/Domain/Interfaces/IEvent.cs

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+namespace IM_API.Domain.Interfaces
+{
+    public interface IEvent
+    {
+    }
+}