Add Kubevirt Port and Instance classes with CURD interfaces

Change-Id: I1afbba8a04bc1872cc1c086f2e3a15620533d517
diff --git a/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/KubevirtInstance.java b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/KubevirtInstance.java
new file mode 100644
index 0000000..83f7a1f
--- /dev/null
+++ b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/KubevirtInstance.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2021-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.kubevirtnetworking.api;
+
+import java.util.Set;
+
+/**
+ * Interface of kubevirt instance.
+ */
+public interface KubevirtInstance {
+
+    /**
+     * Returns the kubevirt instance UID.
+     *
+     * @return kubevirt instance UID
+     */
+    String uid();
+
+    /**
+     * Returns the kubevirt instance name.
+     *
+     * @return kubevirt instance name
+     */
+    String name();
+
+    /**
+     * Returns the kubevirt ports associated with the instance.
+     *
+     * @return kubevirt ports
+     */
+    Set<KubevirtPort> ports();
+
+    interface Builder {
+
+        /**
+         * Builds on immutable instance.
+         *
+         * @return kubevirt instance
+         */
+        KubevirtInstance build();
+
+        /**
+         * Returns instance builder with supplied UID.
+         *
+         * @param uid UID of instance
+         * @return instance builder
+         */
+        Builder uid(String uid);
+
+        /**
+         * Returns instance builder with supplied name.
+         *
+         * @param name name of instance
+         * @return instance builder
+         */
+        Builder name(String name);
+
+        /**
+         * Returns instance builder with supplied ports.
+         *
+         * @param ports set of ports
+         * @return instance builder
+         */
+        Builder ports(Set<KubevirtPort> ports);
+    }
+}