Filters WP_Query arguments when querying posts via the REST API.

The dynamic portion of the hook name, $this->post_type, refers to the post type slug.

Possible hook names include:

• rest_post_query
• rest_page_query
• rest_attachment_query

Enables adding extra arguments or setting defaults for a post collection request.

$args       = apply_filters( "rest_{$this->post_type}_query", $args, $request );