add next preview server route for brd

[tjheffner]

Description

Closes #9886.

Testing done

Screenshots

QA steps

What needs to be checked to prove this works?
What needs to be checked to prove it didn't break any related things?
What variations of circumstances (users, actions, values) need to be checked?

As user uid with user_role

1. Do this
   • Validate that
2. Then
   • Validate that
3. Then validate Acceptance Criteria from issue
   • a
   • b
   • c

Definition of Done

• Documentation has been updated, if applicable.
• Tests have been added if necessary.
• Automated tests have passed.
• Code Quality Tests have passed.
• Acceptance Criteria in related issue are met.
• Manual Code Review Approved.
• If there are field changes, front end output has been thoroughly checked.

Select Team for PR review

• CMS Team
• Public websites
• Facilities
• User support
• Accelerated Publishing

Is this PR blocked by another PR?

• DO NOT MERGE

Does this PR need review from a Product Owner

• Needs PO review

CMS user-facing announcement

Is an announcement needed to let editors know of this change?

• Yes, and it's written in issue ____ and queued for publication.
  • Merge and ping the UX writer so they are ready to publish after deployment
• Yes, but it hasn't yet been written
  • Don't merge yet -- ping the UX writer to write and queue content
• No announcement is needed for this code change.
  • Merge & carry on unburdened by announcements

[github-actions]

GitHub Workflows (.github/workflows/*.yml)

Have you...

• pinned all affected GitHub Actions at a specific commit by SHA?
• reviewed the source code of the action at the commit you are pinning?
• confirmed that no GitHub security measures are being bypassed?
• checked for any injection of user content into protected contexts?
• reviewed Security hardening for GitHub Actions?
• reviewed GitHub Workflows?