Handle Payment Intent requiring additional actions

[FSM1]

When a payment intent is created by the API (eg. the user added a card and paid for month 1 and now the API is attempting to charge them for the 2nd month) and this payment intent requires additional action from the user (Such as providing 3DS authorization) we need to notify the user that there is an outstanding action required, and allow the user to take this action.

An API endpoint to fetch these payment intents will be required, as well as some UI to display these (notification area). Clicking on the notification would bring up the URL specified in the PaymentIntent.nextAction in an iFrame allowing the user to perform any authorization steps required by their bank.