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; }
+    }
+}