Adding ServerSentEvents to Rest Southbound interface

Change-Id: I77411df608be8a1cab9d828db17202f88b969a0f
diff --git a/drivers/server/src/test/java/org/onosproject/drivers/server/RestSBControllerMock.java b/drivers/server/src/test/java/org/onosproject/drivers/server/RestSBControllerMock.java
index 915c1bb..265432b 100644
--- a/drivers/server/src/test/java/org/onosproject/drivers/server/RestSBControllerMock.java
+++ b/drivers/server/src/test/java/org/onosproject/drivers/server/RestSBControllerMock.java
@@ -33,8 +33,10 @@
 import java.util.Set;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Consumer;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;
+import javax.ws.rs.sse.InboundSseEvent;
 
 import static org.hamcrest.Matchers.notNullValue;
 import static org.junit.Assert.assertThat;
@@ -168,8 +170,24 @@
     }
 
     @Override
-     public <T> T post(DeviceId device, String request, InputStream payload,
-            MediaType mediaType, Class<T> responseClass) {
+    public <T> T post(DeviceId device, String request, InputStream payload,
+        MediaType mediaType, Class<T> responseClass) {
         return null;
-     }
+    }
+
+    @Override
+    public void startServerSentEvents(DeviceId deviceId, String eventsUrl) {
+        return;
+    }
+
+    @Override
+    public int getServerSentEvents(DeviceId deviceId, String request,
+                                   Consumer<InboundSseEvent> onEvent, Consumer<Throwable> onError) {
+        return 204;
+    }
+
+    @Override
+    public int cancelServerSentEvents(DeviceId deviceId) {
+        return 200;
+    }
 }
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