Fix missing relationships in entities

Author: jasiekluch

api/src/main/java/com/creatubbles/api/model/notification/CreationEntity.java

@@ -1,11 +1,23 @@
 package com.creatubbles.api.model.notification;
 
 
+import android.support.annotation.NonNull;
+
+import com.creatubbles.api.model.creation.Creation;
+import com.github.jasminb.jsonapi.annotations.Relationship;
 import com.github.jasminb.jsonapi.annotations.Type;
 
 /**
  * @author Pawel Szymanski
  */
 @Type("creation_entities")
 public class CreationEntity extends Entity {
+
+    @Relationship("creation")
+    private Creation creation;
+
+    @NonNull
+    public Creation getCreation() {
+        return creation;
+    }
 }

api/src/main/java/com/creatubbles/api/model/notification/GalleryEntity.java

@@ -1,10 +1,22 @@
 package com.creatubbles.api.model.notification;
 
+import android.support.annotation.NonNull;
+
+import com.creatubbles.api.model.gallery.Gallery;
+import com.github.jasminb.jsonapi.annotations.Relationship;
 import com.github.jasminb.jsonapi.annotations.Type;
 
 /**
  * @author Pawel Szymanski
  */
 @Type("gallery_entities")
 public class GalleryEntity extends Entity {
+
+    @Relationship("gallery")
+    private Gallery gallery;
+
+    @NonNull
+    public Gallery getGallery() {
+        return gallery;
+    }
 }

api/src/main/java/com/creatubbles/api/model/notification/UserEntity.java

@@ -1,10 +1,22 @@
 package com.creatubbles.api.model.notification;
 
+import android.support.annotation.NonNull;
+
+import com.creatubbles.api.model.user.User;
+import com.github.jasminb.jsonapi.annotations.Relationship;
 import com.github.jasminb.jsonapi.annotations.Type;
 
 /**
  * @author Pawel Szymanski
  */
 @Type("user_entities")
 public class UserEntity extends Entity {
+
+    @Relationship("user")
+    private User user;
+
+    @NonNull
+    public User getUser() {
+        return user;
+    }
 }