Remove duplicates member in child classes, add "@OverRide" annotation

Fixes gitlab4j#1255

Author: jmini

gitlab4j-models/src/main/java/org/gitlab4j/api/models/AbstractEpic.java

@@ -34,6 +34,7 @@ public String toValue() {
             return (enumHelper.toString(this));
         }
 
+        @Override
         public String toString() {
             return (enumHelper.toString(this));
         }
@@ -241,6 +242,7 @@ public String getLinkByName(String name) {
         return (links.get(name));
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/AbstractMinimalEpic.java

@@ -77,6 +77,7 @@ public void setUrl(String url) {
         this.url = url;
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/ChildEpic.java

@@ -5,6 +5,7 @@
 public class ChildEpic extends AbstractEpic<ChildEpic> {
     private static final long serialVersionUID = 1L;
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/CreatedChildEpic.java

@@ -7,7 +7,6 @@ public class CreatedChildEpic extends AbstractMinimalEpic<CreatedChildEpic> {
 
     private Boolean hasChildren;
     private Boolean hasIssues;
-    private String url;
     private String relationUrl;
 
     public Boolean getHasChildren() {
@@ -26,14 +25,6 @@ public void setHasIssues(Boolean hasIssues) {
         this.hasIssues = hasIssues;
     }
 
-    public String getUrl() {
-        return url;
-    }
-
-    public void setUrl(String url) {
-        this.url = url;
-    }
-
     public String getRelationUrl() {
         return relationUrl;
     }
@@ -42,6 +33,7 @@ public void setRelationUrl(String relationUrl) {
         this.relationUrl = relationUrl;
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/Epic.java

@@ -49,6 +49,7 @@ public void setSubscribed(Boolean subscribed) {
         this.subscribed = subscribed;
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/EpicInLink.java

@@ -5,6 +5,7 @@
 public class EpicInLink extends AbstractEpic<EpicInLink> {
     private static final long serialVersionUID = 1L;
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/IssueEpic.java

@@ -5,6 +5,7 @@
 public class IssueEpic extends AbstractMinimalEpic<IssueEpic> {
     private static final long serialVersionUID = 1L;
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/RelatedEpic.java

@@ -76,6 +76,7 @@ public void setLinkUpdatedAt(Date linkUpdatedAt) {
         this.linkUpdatedAt = linkUpdatedAt;
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/RelatedEpicLink.java

@@ -63,6 +63,7 @@ public void setUpdatedAt(Date updatedAt) {
         this.updatedAt = updatedAt;
     }
 
+    @Override
     public String toString() {
         return (JacksonJson.toJsonString(this));
     }

gitlab4j-models/src/main/java/org/gitlab4j/api/models/TreeItem.java

@@ -12,6 +12,7 @@ public enum Type {
         BLOB,
         COMMIT;
 
+        @Override
         public String toString() {
             return (name().toLowerCase());
         }