Integrate 404 page template

[joemaller]

Source template which just wraps the default page template:

• https://github.com/ideasonpurpose/nrmp-web/blob/8612e701fdf952a2d6338a97a844e76e6b03aded/wp-content/themes/iop-nrmp/404.php
• https://github.com/ideasonpurpose/NJH002-NJHI-web/blob/802e46c5b90cd53b3a2ac4ef34f2fa9dae97750a/wp-content/themes/iop-njhi/404.php

That will need to be a bit more durable and have some fallbacks in case the page.php template doesn't exist. It should also defer to any existing 404.php template.

This should also expose a wp\Init\NotFound (find a better name) function which would encapsulate all the 404.php logic.

This would then give us a template which looked something like this:

<?php
/**
 * Template name: 404 Page
 */

namespace IdeasOnPurpose;

new WP\Init\NotFound();

get_header();

get_template_part('page');

get_footer();

Possible references:

• https://github.com/tommcfarlin/page-template-example
• https://www.pradipdebnath.com/2019/08/17/how-to-add-page-template-from-plugin-in-wordpress/
• https://rainastudio.com/add-page-template-from-wordpress-plugin/
• https://www.wpexplorer.com/wordpress-page-templates-plugin/