Use MessageKey instead of MessageId

mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/message/MessageId.kt

-package net.mamoe.mirai.message
-
-/**
- * [Message] 在数据包中的 id([UByte])
- *
- * Java 调用方式:
- * MessageId.at
- *
- * @author Him188moe
- */
-object MessageId {
-
-    const val AT: Int = 0x06
-
-    const val FACE: Int = 0x02
-
-    const val TEXT: Int = 0x01
-
-    const val IMAGE: Int = 0x03
-
-    const val CHAIN: Int = 0xff//仅用于 equals. Packet 中不存在 Chain 概念
-}
\ No newline at end of file

mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/message/defaults/Image.kt

 package net.mamoe.mirai.message.defaults
 
 import net.mamoe.mirai.message.Message
-import net.mamoe.mirai.message.MessageId
 import net.mamoe.mirai.message.MessageKey
 import net.mamoe.mirai.network.protocol.tim.packet.*
 import net.mamoe.mirai.utils.lazyDecode
@@ -27,7 +26,7 @@ open class Image(val imageId: String) : Message() {
     }
 
     override fun toByteArray(): ByteArray = lazyEncode { section ->
-        section.writeByte(MessageId.IMAGE)
+        section.writeByte(intValue)
 
         section.writeLVByteArray(lazyEncode { child ->
             child.writeByte(0x02)