Added test file for swagger2.0 and fixed type

[hbina]

1. Also boxed the variants because they are extremely large....I don't want this on the stack.

Signed-off-by: Hanif Bin Ariffin [email protected]

[bergmark]

I'm not sure if this library aims for roundtripping of documents, but it would be great to have a test for roundtripping here. e.g. deserialize to serde_json::Value (a), then to openapi, serialize to serde_json::Value (b), and then compare (a) and (b).