Events are now also implementing Serializable

src/main/java/org/gitlab4j/api/webhook/PushEvent.java

@@ -4,6 +4,7 @@ package org.gitlab4j.api.webhook;
 import org.gitlab4j.api.utils.JacksonJson;
 
 public class PushEvent extends AbstractPushEvent implements Event {
+    private static final long serialVersionUID = 1L;
 
     public static final String X_GITLAB_EVENT = "Push Hook";
     public static final String OBJECT_KIND = "push";

src/main/java/org/gitlab4j/api/webhook/ReleaseEvent.java

@@ -3,6 +3,7 @@ package org.gitlab4j.api.webhook;
 import org.gitlab4j.api.utils.JacksonJson;
 
 public class ReleaseEvent extends AbstractEvent {
+    private static final long serialVersionUID = 1L;
 
     public static final String X_GITLAB_EVENT = "Release Hook";
     public static final String OBJECT_KIND = "release";

src/main/java/org/gitlab4j/api/webhook/TagPushEvent.java

@@ -4,6 +4,7 @@ package org.gitlab4j.api.webhook;
 import org.gitlab4j.api.utils.JacksonJson;
 
 public class TagPushEvent extends AbstractPushEvent implements Event {
+    private static final long serialVersionUID = 1L;
 
     public static final String X_GITLAB_EVENT = "Tag Push Hook";
     public static final String OBJECT_KIND = "tag_push";

src/main/java/org/gitlab4j/api/webhook/WikiPageEvent.java

@@ -4,6 +4,7 @@ import org.gitlab4j.api.models.User;
 import org.gitlab4j.api.utils.JacksonJson;
 
 public class WikiPageEvent extends AbstractEvent {
+    private static final long serialVersionUID = 1L;
 
     public static final String X_GITLAB_EVENT = "Wiki Page Hook";
     public static final String OBJECT_KIND = "wiki_page";