群发消息增加isSendAll属性及相关方法，用于显式指定是否群发消息至所有用户

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/util/json/WxMpMassTagMessageGsonAdapter.java

@@ -24,7 +24,7 @@ public class WxMpMassTagMessageGsonAdapter implements JsonSerializer<WxMpMassTag
     JsonObject messageJson = new JsonObject();
 
     JsonObject filter = new JsonObject();
-    if (null == message.getTagId()) {
+    if (message.isSendAll() || null == message.getTagId()) {
       filter.addProperty("is_to_all", true);
     } else {
       filter.addProperty("is_to_all", false);