Parse .$id and connect with .$ref

[1602]

{
    "$id": "http://localhost:1234/tree",
    "description": "tree of nodes",
    "type": "object",
    "properties": {
        "meta": {
            "type": "string"
        },
        "nodes": {
            "type": "array",
            "items": {
                "$ref": "node"
            }
        }
    },
    "required": [
        "meta",
        "nodes"
    ],
    "definitions": {
        "node": {
            "$id": "http://localhost:1234/node",
            "description": "node",
            "type": "object",
            "properties": {
                "value": {
                    "type": "number"
                },
                "subtree": {
                    "$ref": "tree"
                }
            },
            "required": [
                "value"
            ]
        }
    }
}