PRO-6587: access to fully rendered rich text widgets without giving up all access to other area properties or logging out

[boutell]

…

Summary

See changelog

What are the specific steps to test this change?

• npm link into starter-kit-essentials
• make an inline permalink (not a pasted URL link) to another page, refresh page — it is still recognized as such by the link dialog
• same for inline images in rich text — still recognized as an existing inline image by the editor on next visit
• note the incognito view still fully resolves the URLs of linked pages and inline images (desirable behavior, except in the editor)
• Now, while logged in, use the GET REST API to access the home page at http://localhost:3000/api/v1/@apostrophecms/page/_home
• Note that inline images and permalinks are not fully resolved (appropriate because we might be editing)
• Now add ?render-areas=inline
• Note that each widget now has an additional _rendered property containing fully rendered markup for that widget, including fully resolved inline images and permalinks

What kind of change does this PR introduce?

(Check at least one)

• [X] Bug fix
• [X] New feature
• [ ] Refactor
• [ ] Documentation
• [ ] Build-related changes
• [ ] Other

Make sure the PR fulfills these requirements:

• [X] It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• [X] The changelog is updated
• [ ] Related documentation has been updated
• [ ] Related tests have been updated

If adding a new feature without an already open issue, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[linear[bot]]

PRO-6587 Permalinked pages and inline images need to be converted when consuming documents in Apostrophe Headless