This pull request makes a bunch of changes to the Addons page in the Control Panel.

Addon Listing

Instead of being a not-very-good clone of the Marketplace, the addons index page will now simply list out your installed addons:

Unlisted addons have moved to this page, and will no longer be listed on the "Updates" page.

Addon Settings

This PR also makes it possible for addons to create their own settings pages by providing a "settings blueprint".

Settings blueprints can either be defined in an addon's service provider, or they can live in resources/blueprints/settings.yaml where they'll be automatically picked up.

public function bootAddon()
{
    $this->registerSettingsBlueprint([
        'tabs' => [
            'main' => [
                'sections' => [
                    [
                        'display' => __('SEO Basics'),
                        'fields' => [
                            [
                                'handle' => 'website_name',
                                'field' => ['type' => 'text', 'display' => 'Website Name', 'validate' => 'required'],
                            ],
                            [
                                'handle' => 'google_webmaster_verification_code',
                                'field' => ['type' => 'text', 'display' => 'Google Webmaster Verification Code'],
                            ],
                        ],
                    ],
                ],
            ],
        ],
    ]);
}

Configuration values, like URLs or API Keys can be referenced in addon settings using Antlers: {{ config:app:url }}

Addons can then retrieve their settings via the Addon facade:

use Statamic\Facades\Addon;

$addon = Addon::get('vendor/package');

// Getting settings...
$addon->settings()->get('api_key');

$addon->settings()->all();
$addon->settings()->raw(); // Doesn't evaluate Antlers

// Setting values...
$addon->settings()->set('api_key', '{{ config:services:example:api_key }}');

$addon->settings()->set([
    'website_name' => 'My Awesome Site',
    'api_key' => '{{ config:services:example:api_key }}',
]);

// Saving...
$addon->settings()->save();

By default, addon settings will be stored in YAML files in resources/addons. However, they can easily moved into the database using php please install:eloquent-driver.

Permissions

We now have two sets of addon-related permissions:

• Configure Addons
  • This permission already existed. It'll give you access to view the list of installed addons and edit any addon settings.
• Edit {addon} settings
  • This is a new permission. It gives you access to the settings of a particular addon.
  • When you don't also have the "Configure Addons" permission, addon settings will be available via dedicated nav items, so you don't need to go through the index page.

What's the difference between addon settings & config files?

• Addon Settings are intended to be settings that end-users should be able to touch. Things like SEO defaults or configuring sitemaps.
• Config files are intended to hold settings that only a developer should be touching. Like anything that references classes, or is fundamental to the running of the app.

Related: statamic/docs#1699
Related: statamic/eloquent-driver#469