REST API: Prime post caches in comments in endpoint.

[spacedmonkey]

In the WP_REST_Comments_Controller class, there are multiple calls to the comment's post, why calling get_post like this,

   $post = get_post( (int) $comment->comment_post_ID );

Post caches should be primed using the update_comment_post_cache param.

[spacedmonkey]

Before

[spacedmonkey]

After

Trac ticket: https://core.trac.wordpress.org/ticket/56272

Aside from the CS issue, looks good to merge to me.

[peterwilsoncc]

I think this can go in 6.1.

I've self assigned it for commit as Jonny is AFK for the next few weeks.

[peterwilsoncc]

In 53772:

REST API: Prime post caches in comments endpoint.

Prevent each call to get_post() triggering a seperate database query by priming the cache of each comment's post in
the REST API's comments endpoint.

Props spacedmonkey, timothyblynjacobs.
Fixes #56272.

Committed in https://core.trac.wordpress.org/changeset/53772 (c1cf07e4e30cf0a2fde3f2be0a6983025b3d2062)

[desrosj]

There are a lot of caching API related changes in 6.1 and a dev note should be written collecting them all. Marking this for inclusion.

[spacedmonkey]

Early draft of a dev note can be found ​here.

[milana_cap]

Dev note: ​https://make.wordpress.org/core/2022/10/10/performance-improvements-to-the-rest-api/