Fix the "Transfer to another user" screen in the hosting dashboard

[markbiek]

Fixes ARC-1294

Proposed Changes

Scenario 1
A CIAB user is attempting to transfer a domain mapping to another user on the same CIAB site. In this case, we only see a "-" since no display name is available and the user id is directly from the CIAB site and is not a WPCOM user id.

Scenario 2
A WPCOM user (with a WoA) site is attempting to transfer a domain mapping to another user on the site. The other user was manually created on the site, then attached to a WPCOM account later. In this case, we see the correct display name for the other user but the user id is still directly from the site and is not a WPCOM user id.

The fix
Previously, we called /wp/v2/:siteId/users to populate the "New Owner" pulldown. This (generally) went directly to the remote site.

Now we call the /rest/v1.1/sites/:siteId/users?force=wpcom endpoint. This ensures that we always get the correct WPCOM user data, even in cases like CIAB.

Testing Instructions

• Create a new CIAB site and invite another user to the site.
• Attach an external domain to the site (no need to setup DNS).
• Run this locally or use the calypso.live url and visit /ciab/domains/the.external-domain.com/transfer/other-user.
• Verify that the pulldown contains the correct display name and user id for the other user.

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 tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• 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-164483

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-164483&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-164483&env=a8c-for-agencies

Dashboard live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-164483&env=dashboard

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications
• odyssey-stats
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug ARC-1294/transfer-users-list on your sandbox.

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.