Allow to validate Apache/Nginx configuration requirement for aggregation folder before enabling aggregation.

The idea is to check the response status.
If the server is configured to return the file's content directly without passing a request through the PHP application on an empty file, the status code 404 will be returned.
In other cases, the controller will generate the aggregated file if files exist to aggregate or status code 400 if the aggregation file fails to be generated. In short, a response status code is different from 404.
I provided initial implementation. Feedback is welcome.

Could we also do this for image styles?

Image styles would be amazing as that's bit me before.

Moving to NW for a change record though for the new setting.

brilliant feature! thanks for the development:)

The feature is really great, at this point a note that the patch is not compatible with Drupal 10.2. see details here in the issue: 🐛 system.performance.yml no longer considered after update Closed: works as designed

I received two errors:

admin/config/development/performance|Warning: Undefined variable $config in Drupal\system\Form\PerformanceForm->buildForm() (line 170 of d10.2.x/html/core/modules/system/src/Form/PerformanceForm.php

admin/reports/status|1||Error: Call to a member function get() on null in Drupal\system\Form\PerformanceForm->buildForm() (line 170 of d10.2.x/html/core/modules/system/src/Form/PerformanceForm.php)

Thanks for the feedback. Adding new form elements to the config form was not the best idea.
So, I removed the validation button and performed validation on the appropriate checkbox checked change state.
Please review.

Regarding #5: I filled the follow-up issue ✨ Allow to validate Apache/Nginx configuration for image style files access Active for image style validation as it requires a different approach and different change scope to implement the new validation feature.

test cases using different NGINX_VHOST_PRESET env var in Docker4Drupal development stack:
- drupal9 or drupal8 validation will show the warning regarding server requirement;
- drupal10 validation will show that server configured properly

In case you need to apply the patch for a 10.1.x Drupal you can find the patch attached 😇

Believe next step would be to get test coverage added.

it would be nice to know which tests are failing

I get a js error in the console and this error in my logs:

https://mysite/css/_validate.css|https://mysite/admin/config/development/performance|1||Symfony\Component\HttpKernel\Exception\BadRequestHttpException: The theme must be passed as a query argument in Drupal\system\Controller\AssetControllerBase->deliver() (line 132 of d10.2.x/html/core/modules/system/src/Controller/AssetControllerBase.php).

Adding the current state of the MR so that I can use it from composer patches securely.