[5.x] Add config extra sections with fields to existing fieldtypes

[nopticon]

After reading https://statamic.dev/extending/fieldtypes#adding-configuration-fields-to-existing-fieldtypes I noticed that extra sections are not added to fieldtype config.

use Statamic\Fieldtypes\Text;

Text::appendConfigFields([
    [
        'display' => __('Extra section'),
        'fields' => [
            'more_options' => [
                'display' => __('Options'),
                'instructions' => __('Instructions for this field'),
                'type' => 'array',
            ],
        ],
    ],
]);

Before this fix, it shows like this:

After fixing this issue, it shows fields inside the new section:

After adding appendConfigFields to a ServiceProvider, it can be tested on any blueprint at /cp/collections/{collection}/blueprints/{blueprint}/edit

This PR adds extra sections support to #5077 and #7706

[nopticon]

Hi Duncan! This PR does not add a new method, just enhances how the existing "appendConfigFields" method handles the array when it contains the "fields" key. Please let me know if any questions.

[duncanmcclean]

Sorry, ignore me! 🙈

I was reading #5077 and saw extendConfigFields but didn't realise the method name got changed to appendConfigFields before it was merged.

[duncanmcclean]

Are you able to add a test for this? It can go in tests/Fields/FieldtypeTest.php.

[nopticon]

Ok will do!