Add confirmation screen for authenticated user who only requests notification for unsupported services

[markmhendrickson]

This entails adding a confirmation screen to the end of the cart flow for authenticated users who have selected only unsupported services.

Currently, the user is shown the default homepage but instead should be shown a message to the extent of "Thanks for your interest, we'll be in touch" similar to what we show for users who have just verified their contact in order to request notification.