ari: Allow variables to be set on channel create.

This change adds the same variable functionality that
is available for originating a channel to the create
call. Now when creating a channel you can specify
dialplan variables to set instead of having to do another
API call.

ASTERISK-28896

Change-Id: If13997ba818136d7c070585504fc4164378aa992

rest-api/api-docs/channels.json

@@ -222,6 +222,14 @@
 							"required": false,
 							"allowMultiple": false,
 							"dataType": "string"
+						},
+						{
+							"name": "variables",
+							"description": "The \"variables\" key in the body object holds variable key/value pairs to set on the channel on creation. Other keys in the body object are interpreted as query parameters. Ex. { \"endpoint\": \"SIP/Alice\", \"variables\": { \"CALLERID(name)\": \"Alice\" } }",
+							"paramType": "body",
+							"required": false,
+							"dataType": "containers",
+							"allowMultiple": false
 						}
 					],
 					"errorResponses": [