[CHORE] Checkout Notifications

Status
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**READY**


Description
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Provide error messages for invalid forms and notifications for coupon entry. Prevent payment button from submitting until delivery options are chosen.


Purpose
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- [x] Disable coupon code entry until address has been entered
- [x] Provide a notice if coupon code has been successfully applied
- [x] Provide error notices if coupon code cannot be applied
- [x] Prevent pay button from submitting until order is in 'payment' state
- [x] Add shake effect and error message to button instead of disabling it if forms are invalid


Deploy Notes
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None.