Support url-compound-parameter

[fklebert]

At the moment, https://github.com/ndsev/zswag#url-compound-parameter is not supported.
It would be handy to be able to use compound parts of the request object in a path for example.
For this we would need the possibility to get a URL encoded string of the compound object which we then can map to a certain piece of the path. So if it is only about a 100% match of a compound object (e.g. a header structure) that would work great, no need to flatten things further.
The actual problem that I would like to target is to be able to map a request object which consists out of a scalar ID and a more complex header structure to a path of /{id}/{url_encoded_blob}

My understanding of zswag as now is that I can only url-encode the complete request object so that the ID cannot be mapped individually which kind of affects the backend more than necessary in terms of deployment.