Missing coupon functionality: codeless coupons, `applies_to` parameter

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While working on adding coupons we recently ran into a couple issues that forced us to create the coupons via the dashboard rather than use Terraform:

• there's no way to create codeless coupons from what I could tell?
• there's no support for the applies_to parameter

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And as soon as I post this, I notice #43 🙈