D10+ Multi-Domain and Multisite support

Hello,

We need this on our project so I worked on it and just created an issue fork.
I just added a "Use domain" field on configuration form and then use that in BoostCacheFile.php prepend (or not) the current domain to the uri.

We used that on some test site and it works, with or without domain cache files are created when visiting pages.

One inconsistency though is that when purging in admin interface it is purging every files for every domain while for generating files it generates only for current domain. So one improvement would be to harmonize how it is working there, or give possibility to generate or purge by domain or for all at once (but requires boost to know for which domains to generate cache files)

Path Generation:

// In BoostCache.php or similar
protected function getCachePath() {
  $base_path = parent::getCachePath();
  if ($this->config->get('multisite_support')) {
    $base_path = $base_path . '/' . \Drupal::request()->getHost();
  }
  return $base_path;
}

Settings Form Addition:

// In BoostSettingsForm.php
$form['multisite'] = [
  '#type' => 'details',
  '#title' => $this->t('Multisite settings'),
  '#open' => FALSE,
];

$form['multisite']['enable_domain_paths'] = [
  '#type' => 'checkbox',
  '#title' => $this->t('Enable domain-specific cache paths'),
  '#default_value' => $config->get('enable_domain_paths'),
  '#description' => $this->t('When enabled, each domain will get its own cache subdirectory.'),
];

Thanks abhishek@kumar,

I have already done similar changes in the issue fork.
I'd like to have maintainers feedback before making a merge request or imprivement. Or maybe I should make it a merge request to get feedback?

For consistency I have also edited getCachedFiles() to get only cached files by domain and be more precise in the description of the use_domain configuration field.

Now when using domain:
- Cache files are separated in domain related directories
- Purge and Generation works only on domain you are currently logged in.

I have just noticed while writing this, that the purge on boost_cron() method will work only on base domain so I still have to work on this.

If just creating a directory by domain is enough for this to be a feature then this merge request is ready for review and I've made a patch out of it.

After applying the patch and set up at least two domains pointing on the same drupal installation and visiting them, boost cache file directory will be split between directories named after your domains.