What can you do with SiteConfiguration in TYPO3 and how to get a site object from anywhere?

SiteFactory.php

<?php
declare(strict_types=1);
namespace Vendor\Extension\Factory;

use GuzzleHttp\Psr7\Uri;
use TYPO3\CMS\Core\Exception\SiteNotFoundException;
use TYPO3\CMS\Core\Http\Request;
use TYPO3\CMS\Core\Http\ServerRequest;
use TYPO3\CMS\Core\Routing\SiteMatcher;
use TYPO3\CMS\Core\Site\Entity\Site;
use TYPO3\CMS\Core\Site\SiteFinder;
use TYPO3\CMS\Core\Utility\GeneralUtility;

/**
 * Class SiteFactory
 * with some examples how to get a site object anywhere
 */
class SiteFactory
{
    /**
     * Try to find a matching site from a given url (e.g. a deeplink)
     *
     * @param string $url
     * @return Site
     */
    public function getSiteFromUrl(string $url = 'https://domain.org/path/path/'): Site
    {
        $uri = GeneralUtility::makeInstance(Uri::class, $url);
        $request = GeneralUtility::makeInstance(ServerRequest::class, $uri);
        $matcher = GeneralUtility::makeInstance(SiteMatcher::class);
        $routeResult = $matcher->matchRequest($request);
        return $routeResult->getSite();
    }

    /**
     * Get fitting site from a page identifier
     *
     * @param int $pageIdentifier
     * @return Site
     * @throws SiteNotFoundException
     */
    public function getSiteFromPageIdentifier(int $pageIdentifier = 123): Site
    {
        $siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
        return $siteFinder->getSiteByPageId($pageIdentifier);
    }

    /**
     * Get site from a root page identifier
     *
     * @param int $rootpageIdentifier
     * @return Site
     * @throws SiteNotFoundException
     */
    public function getSiteByRootpageIdentifier(int $rootpageIdentifier = 123): Site
    {
        $siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
        return $siteFinder->getSiteByRootPageId($rootpageIdentifier);
    }

    /**
     * Get first defined site configuration
     *
     * @return Site
     */
    public function getFirstSite(): Site
    {
        $siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
        $sites = $siteFinder->getAllSites();
        return array_values($sites)[0];
    }

    /**
     * Get site from a request object
     *
     * @param Request $request
     * @return Site
     */
    public function getSiteFromRequest(Request $request): Site
    {
        return $request->getAttribute('site');
    }
}

SiteHelper.php

<?php
declare(strict_types=1);
namespace Vendor\Extension\Helper;

use TYPO3\CMS\Core\Site\Entity\Site;
use TYPO3\CMS\Core\Utility\ArrayUtility;

/**
 * Class SiteHelper
 * with some examples how to play with it
 */
class SiteHelper
{
    /**
     * Build a link to a page by given page identifier
     *
     * @param int $pageIdentifier
     * @param Site $site
     * @return string
     */
    public function buildUrlToPage(int $pageIdentifier, Site $site): string
    {
        $uri = $site->getRouter()->generateUri($pageIdentifier);
        return $uri->__toString();
    }

    /**
     * Build a link to a page by given page identifier and any parameters (like typeNum)
     *
     * @param int $pageIdentifier
     * @param array $arguments
     * @param Site $site
     * @return string
     */
    public function buildUrlToPageWithArguments(int $pageIdentifier, array $arguments = ['type' => 98], Site $site): string
    {
        $uri = $site->getRouter()->generateUri($pageIdentifier, $arguments);
        return $uri->__toString();
    }

    /**
     * Get the root page identifier
     *
     * @param Site $site
     * @return int
     */
    public function getRootpageIdentifier(Site $site): int
    {
        return $site->getRootPageId();
    }

    /**
     * Get any configuration from site object
     *
     * Example with your individual configuration in site yaml:
     *      rootPageId: 1
     *      base: https://domain.org
     *      myProject:
     *          recordStorage: 123
     *
     * @param string $configurationPath
     * @param Site $site
     * @return string|int|array
     */
    public function getConfigurationFromSite(Site $site, string $configurationPath = 'myProject.recordStorage')
    {
        $array = $site->getConfiguration();
        return ArrayUtility::getValueByPath($array, $configurationPath, '.');
    }

    /**
     * Get the default language identifier
     *
     * @param Site $site
     * @return int
     */
    public function getDefaultLanguageId(Site $site): int
    {
        return $site->getDefaultLanguage()->getLanguageId();
    }

    /**
     * Get all language configurations (with all properties)
     *
     * @param Site $site
     * @return array
     */
    public function getAllLanguages(Site $site): array
    {
        return $site->getAllLanguages();
    }
}