添加获取单条消息的接口

common/src/main/java/cn/wildfirechat/pojos/InputMessageUid.java

@@ -0,0 +1,12 @@
+package cn.wildfirechat.pojos;
+
+public class InputMessageUid {
+    public long messageUid;
+
+    public InputMessageUid() {
+    }
+
+    public InputMessageUid(long messageUid) {
+        this.messageUid = messageUid;
+    }
+}