Add last changed cache helper function

[tillkruess]

As mentioned in https://core.trac.wordpress.org/ticket/37464#comment:17 and in https://core.trac.wordpress.org/ticket/57625#comment:6

This PR adds the wp_cache_set_last_changed()

function to fire the wp_cache_set_last_changed action when a cache group's last_changed timestamp was updated.

This is a follow up to #4077 as suggest by @peterwilsoncc and @JJJ.

This PR adds the wp_cache_set_last_changed() function to fire the wp_cache_set_last_changed action when a cache group's last_changed timestamp was updated.

Trac ticket: https://core.trac.wordpress.org/ticket/57905

@spacedmonkey Done! https://core.trac.wordpress.org/ticket/57905

Thanks @tillkruss, Left some nit-pick feedback.

Thanks. Should I always use the version number, instead of n.e.x.t?

This is pretty much what I was thinking, does this need an update following ​82cd434?

I don't think so, because the groups won't change. posts last-changed will be stored in post-queries group.

[peterwilsoncc]

The linked pull request looks good to me, let's try to get this in 6.3.

It would be good to get some tests in too, both direct and indirect.

Indirect tests would be to ensure the action fires when inserting/updating/deleting objects that bump the last changed value.

@tillkruss This PR needs to be rebased after. ​https://github.com/WordPress/wordpress-develop/commit/19bd759db57b4f1cc72157a446915ffbafdd838e. I will re-review after this is done.

@peterwilsoncc @SergeyBiryukov Any more input on this?

[spacedmonkey]

In 55702:

Cache API: Add helper function wp_cache_set_last_changed.

Add a helper function called wp_cache_set_last_changed to set the last changed value for cache groups. This function has a new action called wp_cache_set_last_changed, allowing for developers to cache invalidate when last changed value is changed.

Props tillkruess, spacedmonkey, peterwilsoncc, mukesh27, johnjamesjacoby.
Fixes #57905.

I think this is ready to be merged. Any feedback @SergeyBiryukov?

Committed ​https://github.com/WordPress/wordpress-develop/commit/73dbbe53723651bc78dec24b0a075c63e28322a5

[flixos90]

Covered in dev note ​https://make.wordpress.org/core/2023/07/17/improvements-to-the-cache-api-in-wordpress-6-3/

[spacedmonkey]

#58656 was marked as a duplicate.

[spacedmonkey]

#45662 was marked as a duplicate.