Adding ITopicsRepository Interface

register-core/src/main/java/org/opengroup/osdu/register/provider/interfaces/subscriber/ITopicsRepository.java

+package org.opengroup.osdu.register.provider.interfaces.subscriber;
+
+import org.opengroup.osdu.core.common.model.notification.Topic;
+
+import java.util.List;
+
+public interface ITopicsRepository {
+    List<Topic> listMessages();
+}

register-core/src/main/java/org/opengroup/osdu/register/subscriber/persistence/TopicsRepository.java

@@ -22,6 +22,7 @@ import org.apache.http.HttpStatus;
 import org.opengroup.osdu.core.common.logging.JaxRsDpsLog;
 import org.opengroup.osdu.core.common.model.http.AppException;
 import org.opengroup.osdu.core.common.model.notification.Topic;
+import org.opengroup.osdu.register.provider.interfaces.subscriber.ITopicsRepository;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.stereotype.Repository;
@@ -33,7 +34,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 @Repository
-public class TopicsRepository {
+public class TopicsRepository implements ITopicsRepository {
 
     @Autowired
     private JaxRsDpsLog log;

register-core/src/main/java/org/opengroup/osdu/register/subscriber/services/AvailableTopics.java

@@ -18,6 +18,7 @@ package org.opengroup.osdu.register.subscriber.services;
 
 import com.google.common.base.Strings;
 import org.opengroup.osdu.core.common.model.notification.Topic;
+import org.opengroup.osdu.register.provider.interfaces.subscriber.ITopicsRepository;
 import org.opengroup.osdu.register.subscriber.persistence.TopicsRepository;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
@@ -29,7 +30,7 @@ import java.util.stream.Collectors;
 public class AvailableTopics {
 
     @Autowired
-    private TopicsRepository topicRepo;
+    private ITopicsRepository topicRepo;
 
     public boolean exists(String name) {
         if (Strings.isNullOrEmpty(name))