Show promotional blurb when applicable

What does this MR do and why?

Shows a promotional blurb when applicable on summary pane on checkout page in purchase flow.

Please see this MR for the related issue.

Screenshots or screen recordings

Screenshots can be found here.

How to set up and validate locally

Steps to validate the changes can be found here.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.