Added ARI resource /ari/asterisk/ping

Added ARI resource.
GET /ari/asterisk/ping : It returns "pong" message with timestamp
and asterisk id. It would be useful for simple heath check.

Change-Id: I8d24e1dcc96f60f73437c68d9463ed746f688b29

rest-api/api-docs/asterisk.json

@@ -178,6 +178,18 @@
 				}
 			]
 		},
+		{
+			"path": "/asterisk/ping",
+			"description": "Asterisk ping",
+			"operations": [
+				{
+					"httpMethod": "GET",
+					"summary": "Response pong message.",
+					"nickname": "ping",
+					"responseClass": "AsteriskPing"
+				}
+			]
+		},
 		{
 			"path": "/asterisk/modules",
 			"description": "Asterisk modules",
@@ -604,6 +616,27 @@
 				}
 			}
 		},
+		"AsteriskPing": {
+			"id": "AsteriskPing",
+			"description": "Asterisk ping information",
+			"properties": {
+				"asterisk_id": {
+					"required": true,
+					"type": "string",
+					"description": "Asterisk id info"
+				},
+				"ping": {
+					"required": true,
+					"type": "string",
+					"description": "Always string value is pong"
+				},
+				"timestamp": {
+					"required": true,
+					"type": "string",
+					"description": "The timestamp string of request received time"
+				}
+			}
+		},
 		"Module": {
 			"id": "Module",
 			"description": "Details of an Asterisk module",