DIFM: redirect using siteId instead of siteSlug

[aneeshd16]

Related to #94517

Proposed Changes

• After purchasing a DIFM product, redirect to /start/site-content-collection/website-content?siteId=<siteId> instead of /start/site-content-collection/website-content?siteSlug=<siteSlug> after checkout.

Why are these changes being made?

The bug described in #94517 can be replicated by:

• Adding the eCommerce plan to the cart (but not purchasing the product so that it stays in the cart) and then purchasing DIFM for the same site. Since the eCommerce plan is already in the cart, the user can purchase DIFM + eCommerce.

• After purchase, the user is redirected to /start/site-content-collection/website-content?siteSlug=<siteSlug> where siteSlug is the *.wordpress.com subdomain.

• At the same time, atomic transfer happens and the site is switched to a *.wpcomstaging.com subdomain.

• In Calypso, we cannot fetch the correct site slug, so the endpoint sends a request with a null value for the siteSlug.
  

• If we redirect to /start/site-content-collection/website-content?siteId=<siteId>, this issue does not happen as the siteId is constant and available to use immediately.

Testing Instructions

• Follow the steps described in Purchasing the Commerce plan and DIFM Express breaks the connection to DIFM Express tools #94517.
• You should be able to save and submit the form.

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 UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• 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-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-134548

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-134548&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-134548&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~8 bytes added 📈 [gzipped])

name                        parsed_size           gzip_size
update-design-flow                +62 B  (+0.0%)       +8 B  (+0.0%)
signup                            +62 B  (+0.0%)       +8 B  (+0.0%)
home                              +62 B  (+0.0%)       +8 B  (+0.0%)
async-step-unified-plans          +62 B  (+0.0%)       +8 B  (+0.0%)
async-step-unified-domains        +62 B  (+0.0%)       +8 B  (+0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Async-loaded Components (~2 bytes added 📈 [gzipped])

name                                 parsed_size           gzip_size
async-load-signup-steps-page-picker        +18 B  (+0.0%)       +2 B  (+0.0%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.