Refactor of UpfProgrammable APIs

Change-Id: I792659ad4a163d7115d7320bb33c11534edd484a
Signed-off-by: Daniele Moro <daniele@opennetworking.org>
(cherry picked from commit a57652d92bdd01b1e77bffbac78a44f96fb385f3)
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java
new file mode 100644
index 0000000..7ec3b19
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java
@@ -0,0 +1,49 @@
+/*
+ * 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.net.behaviour.upf;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Type of UPF entity.
+ */
+@Beta
+public enum UpfEntityType {
+    INTERFACE("interface"),
+    TERMINATION_DOWNLINK("termination_downlink"),
+    TERMINATION_UPLINK("termination_uplink"),
+    SESSION_DOWNLINK("session_downlink"),
+    SESSION_UPLINK("session_downlink"),
+    TUNNEL_PEER("tunnel_peer"),
+    COUNTER("counter");
+
+    private final String humanReadableName;
+
+    UpfEntityType(String humanReadableName) {
+        this.humanReadableName = humanReadableName;
+    }
+
+    /**
+     * Returns a human readable representation of this UPF entity type (useful
+     * for logging).
+     *
+     * @return string
+     */
+    public String humanReadableName() {
+        return humanReadableName;
+    }
+}