emails/ui/setup/setups/02_api.php

<?php
use Psr\Container\ContainerInterface;

return [
    Psr\Http\Client\ClientInterface::class => function(ContainerInterface $container) {
        return new GuzzleHttp\Client([
            'base_uri' => $container->get('urls')->api,
            'headers' => [
                'Authorization' => [
                    "Bearer {$container->get('api_key')}"
                ]
            ]
        ]);
    },
    Psr\Http\Message\RequestFactoryInterface::class => function(ContainerInterface $container) {
        return $container->get(Nyholm\Psr7\Factory\Psr17Factory::class);
    },
];