Discount Coupons API

[lxalln]

It looks like the Discount Coupons API is not yet implemented.

Is there any reason why I shouldn't have a crack at it and submit a PR?

I assume following the existing pattern of code should be fine. Creating a partial class EcwidClientDiscountCoupons.

From what I can see I won't be able to implement the 'real' tests, as the mocky api will need to be set up.

[kroniak]

You are fully free to submit this PR.

Look at interfaces. partial class is good idea.
You can use testhttp class from Flurl to make test env.

[kroniak]

And please use a dev branch to PR.