Add support for POST requests

[roryf]

I started looking to add support for the listBatchSubscribe method but this really requires a POST request with parameters sent via message body (and support for array parameters, but that's easier done).

It seems like an implementation of IRequestProvider is the way to go about this. What would be the best way to configure a particular method to use the POST provider?

I was thinking of updating HandlesAttribute to also specify an optional RequestType, defaulting to UniversalRequestProvider. Does that sound reasonable?

[ChrisMissal]

This is definitely doable. I can imagine a couple ways to make it happen, but I like your idea. 👍