Parser tests + fix for trait deserialisation.

[JohnRCatlin]

Hi,

Thanks for sharing your java based AsyncAPI parser; very useful. 👍

I've been exploring it with some unit tests (added) and found a couple of issues.
I've applied a fix for trait deserialisation.

You'll notice that one of the tests fails ... highlighting an issue with the jackson json deserialiser, where it interprets the values on and off to true and false in the streetlights.yml. If these are wrapped in parenthesis then it parses them correctly (but I guess we can't rely on that as the the streetlights.yml seems to comply with the AsyncAPI spec).

See the comments in the test ..

// TODO is this a bug?
// The jackson parser seems to convert the values on and off to true and false.
// It interprets them correctly if we use 'on' and 'off' (see streetlights2.yml).
//System.out.println(schema2.getProperties().get("command"));
assertTrue(schema2.getProperties().get("command").getEnum().contains("on"));
assertTrue(schema2.getProperties().get("command").getEnum().contains("off"));