[Milky] make next_.*_seq optional in case of encountering the end (SaltifyDev/milky@91cb6ec)

Author: NoirHare

Lagrange.Milky/Api/Handler/Message/GetHistoryMessagesHandler.cs

@@ -30,7 +30,7 @@ public async Task<GetHistoryMessagesResult> HandleAsync(GetHistoryMessagesParame
             _ => throw new NotSupportedException(),
         };
 
-        return new GetHistoryMessagesResult(messages.Select(_convert.MessageBase), start - 1);
+        return new GetHistoryMessagesResult(messages.Select(_convert.MessageBase), start - 1 > 0 ? start - 1 : null);
     }
 }
 
@@ -51,11 +51,11 @@ public class GetHistoryMessagesParameter(string messageScene, long peerId, long?
     public int Limit { get; } = limit;
 }
 
-public class GetHistoryMessagesResult(IEnumerable<MessageBase> messages, long nextMessageSeq)
+public class GetHistoryMessagesResult(IEnumerable<MessageBase> messages, long? nextMessageSeq)
 {
     [JsonPropertyName("messages")]
     public IEnumerable<MessageBase> Messages { get; init; } = messages;
 
     [JsonPropertyName("next_message_seq")]
-    public long NextMessageSeq { get; init; } = nextMessageSeq;
+    public long? NextMessageSeq { get; init; } = nextMessageSeq;
 }