Use a purpose-built robust slug record to help resolve old links

[ssddanbrown]

Describe the feature you'd like

Currently we resolve old page URLs by checking up the revisions and using their slugs to help locate changed/moved pages.

Revisions though may be cleared, and this system is limited in scope (to page links).
It would be better to create a purpose-built system for this, which tracks slugs off all entity types (pages, chapters, books, shelves) to provide a more reliable fall-back lookup for all.

Describe the benefits this would bring to existing BookStack users

• Greater confidence in external links working over time, and better experience when encountering less broken links.
• Keeps links working to books/chapters/pages that have name changes.

Can the goal of this request already be achieved via other means?

This is the simplest implementation idea really to make things more robust.
Otherwise it's a pain to do this without a lot of manual tracking, or more added logical theme system implementation (which is possible but this should really be in core).

Have you searched for an existing open/closed issue?

• I have searched for existing issues and none cover my fundamental request

How long have you been using BookStack?

Over 5 years

Additional context

As discussed in #3520. Related to many other URL based issues also I think.

[ajmarinmedina]

In addition to the system to manage these URLs, wouldn't it be a good idea to be able to easily modify the original slug? Perhaps there has been a title change but a shorter URL is desired. Something like Wordpress does, which allows you to decide whether or not you want to change the slug.

[ssddanbrown]

Added via #5913, to be part of the next feature release.

@ajmarinmedina There's an existing separate request for that here: #3902