julienmonnerie/kirby/config/api/routes/system.php

<?php

use Kirby\Exception\Exception;
use Kirby\Exception\InvalidArgumentException;

/**
 * System Routes
 */
return [

	[
		'pattern' => 'system',
		'method'  => 'GET',
		'auth'    => false,
		'action'  => function () {
			$system = $this->kirby()->system();

			if ($this->kirby()->user()) {
				return $system;
			}

			$info = match ($system->isOk()) {
				true  => $this->resolve($system)->view('login')->toArray(),
				false => $this->resolve($system)->view('troubleshooting')->toArray()
			};

			return [
				'status' => 'ok',
				'data'   => $info,
				'type'   => 'model'
			];
		}
	],
	[
		'pattern' => 'system/method-test',
		'method'  => 'PATCH',
		'action'  => function () {
			return [
				'status' => match ($this->kirby()->request()->method()) {
					'PATCH' => 'ok',
					default => 'fail'
				}
			];
		}
	],
	[
		'pattern' => 'system/register',
		'method'  => 'POST',
		'action'  => function () {
			return $this->kirby()->system()->register($this->requestBody('license'), $this->requestBody('email'));
		}
	],
	[
		'pattern' => 'system/install',
		'method'  => 'POST',
		'auth'    => false,
		'action'  => function () {
			$system = $this->kirby()->system();
			$auth   = $this->kirby()->auth();

			// csrf token check
			if ($auth->type() === 'session' && $auth->csrf() === false) {
				throw new InvalidArgumentException('Invalid CSRF token');
			}

			if ($system->isOk() === false) {
				throw new Exception('The server is not setup correctly');
			}

			if ($system->isInstallable() === false) {
				throw new Exception('The Panel cannot be installed');
			}

			if ($system->isInstalled() === true) {
				throw new Exception('The Panel is already installed');
			}

			// create the first user
			$user  = $this->users()->create($this->requestBody());
			$token = $user->login($this->requestBody('password'));

			return [
				'status' => 'ok',
				'token'  => $token,
				'user'   => $this->resolve($user)->view('auth')->toArray()
			];
		}
	]

];