Try/custom statuses

[imath]

Description

This is a suggestion to bring custom statuses into the WordPress block editor and contribute to the #3144 issue.

There are 2 commits into this PR. I really think the first one should be considered to be merged as it stops using hardcoded "visibilities" in favor of a new Core/Data Entity: Statuses thanks to the REST route /wp/v2/statuses?context=edit.

I think this first step is important to be able to bring custom statuses into the block editor.

The second commit is trying to actually manage these custom statuses. For instance, if you use this PHP code:

function custom_statuses_register_members_restricted() {
	register_post_status( 'restricted',
		array(
			'label'                     => _x( 'Restricted to members', 'post status', 'text-domain' ),
			'public'                    => true,
			'label_count'               => _n_noop( 'Restricted to members <span class="count">(%s)</span>', 'Restricted to members <span class="count">(%s)</span>', 'text-domain' ),
			'show_in_admin_all_list'    => true,
			'show_in_admin_status_list' => true,
			/* This part is needed by the Block Editor */
			'visibility'                => (object) array(
				'value' => 'restricted',
				'label' => __( 'Restricted to members', 'text-domain' ),
				'info'  => __( 'Only logged in members can view this post.', 'text-domain' ),
			),
		)
	);
}
add_action( 'init', 'custom_statuses_register_members_restricted' );

Here's how the Editor's Post Visibility component will evolve:

How has this been tested?

I've tested the code in WordPress trunk, Gutenberg master and using npm run test-unit to make sure It has no impact on other areas of the Editor.

Screenshots

See above.

Types of changes

New feature (non-breaking change which adds functionality)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.

[youknowriad]

Doing some repository cleanup. A lot has changed since this PR was open (sorry we didn't get to review it properly on time) but it seems that at this point, if we ever want to get to it, it will need to be redone entirely. So I think it's just better to close it for now. Thanks for the efforts.