Add REST API for openstackvtap app

Change-Id: I5d7697069d804eeb88eb57cbd845af90764c7a86
diff --git a/apps/openstackvtap/api/src/main/java/org/onosproject/openstackvtap/api/Constants.java b/apps/openstackvtap/api/src/main/java/org/onosproject/openstackvtap/api/Constants.java
new file mode 100644
index 0000000..f823b7d
--- /dev/null
+++ b/apps/openstackvtap/api/src/main/java/org/onosproject/openstackvtap/api/Constants.java
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.openstackvtap.api;
+
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Provides constants used in OpenstackVtap.
+ */
+public final class Constants {
+
+    private Constants() {
+    }
+
+    public static final String REST_UTF8 = StandardCharsets.UTF_8.name();
+}