Improve the types surfaced by the models

Having worked wit the docker .net API for a while, something I noticed is that certain classes have types I wouldn't expect. For example, the PortBinding class has strings for all it's members, when it returns an IP address and a port. Could these be surfaced as an integer and IP address respectively? Also, I notice this class returns the type of port, this would be really nice as an enum.
I'm happy to look at doing the work ot make this happen if it would be accepted.

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