Update coupon restrictions on blur #223
Description
Our coupon UI has caught me in the past, and I just realized it caught me again. When filling out a coupon's details, the customer subscription piece requires manually hitting the +, which is extremely non-obvious (to me, at least). (I didn't realize I didn't restrict a past coupon until just now when it was conflicting on applying with another coupon I just set up, which also didn't actually have a subscription restriction on it like I thought.)
Per Slack discussion, @adamjudd suggested adding the input on blur.
This should happen for customer subscription restrictions, product code restrictions, and (imo) any other similar UI.
