create undocumented message bot events

slack-api-model/src/main/java/com/slack/api/model/event/MessageBotAddEvent.java

@@ -0,0 +1,30 @@
+package com.slack.api.model.event;
+
+import lombok.Data;
+
+/**
+ * https://api.slack.com/events/message/bot_add
+ * (undocumented)
+ */
+@Data
+public class MessageBotAddEvent implements Event {
+
+  public static final String TYPE_NAME = "message";
+  public static final String SUBTYPE_NAME = "bot_add";
+
+  private final String type = TYPE_NAME;
+  private final String subtype = SUBTYPE_NAME;
+
+  private String botId;
+  private String user;
+
+  private String channel;
+
+  private String text;
+  private String botLink;
+
+  private String ts;
+
+  private String eventTs;
+  private String channelType;
+}

slack-api-model/src/main/java/com/slack/api/model/event/MessageBotRemoveEvent.java

@@ -0,0 +1,30 @@
+package com.slack.api.model.event;
+
+import lombok.Data;
+
+/**
+ * https://api.slack.com/events/message/bot_remove
+ * (undocumented)
+ */
+@Data
+public class MessageBotRemoveEvent implements Event {
+
+  public static final String TYPE_NAME = "message";
+  public static final String SUBTYPE_NAME = "bot_remove";
+
+  private final String type = TYPE_NAME;
+  private final String subtype = SUBTYPE_NAME;
+
+  private String botId;
+  private String user;
+
+  private String channel;
+
+  private String text;
+  private String botLink;
+
+  private String ts;
+
+  private String eventTs;
+  private String channelType;
+}