Support validation enum of properties.

[connor]

If I have a schema with the following properties:

{
    "action_type": {
        "type": "integer",
        "enum": [
            { "default": 1, "description": "foobar" }
        ]
    }
}

And a model is attempting to be generated with the following dictionary:

{
    "action_type": 2
}

(i.e. one where the value that is attempting to be generated is not contained within the values the properties define)

I would expect something to be logged and for the model to not be generated.