#7893065 Golden Token: create constants and a plan description for it

Proposed Changes

• Add constants and a plan description to Calypso so the app properly supports the plan. Without this, users won’t be able to use either Backup or Scan from Calypso, and some UI will represent the plan incompletely.

Testing Instructions

Prerequisites:

• Create a Jetpack site.
• Provision the site with a Golden Token.

Instructions:

• Download this PR.
• Run yarn start.
• Visit http://calypso.localhost:3000/backup/[site] and verify you the service is working on your site.
• Visit http://calypso.localhost:3000/scan/[site] and verify you the service is working on your site.
• Visit http://calypso.localhost:3000/activity-log/[site] and verify you can use the Activity Log.
• Vitis http://calypso.localhost:3000/my-plan/[site] and verify you see the correct icon for the plan.

Demo

My Plan

Backup

Scan

Plans

My purchases

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the “[Status] Needs Privacy Updates” label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?