Whoops: Allow Exceptions to send custom HTTP code

[lukasbestle]

Describe the PR

Whoops overrides any sent HTTP code with its own HTTP 500 unless disabled. This meant that any JSON error response would have HTTP 500 even if the Exception has defined a different code.

It's still the same with the HTML output, but here it's more difficult to set a custom code as we don't have dynamic access to the handled Exception.

Ready?

• Added unit tests for fixed bug/feature Automated Whoops tests are not possible
• Added in-code documentation (if needed)
• CI passes (runs automatically when the PR is created or run composer ci locally)
  Running locally requires PHPUnit, PHP-CS-Fixer, Psalm, PHPCPD and PHPMD.

• Checked whether the PR needs documentation, if needed added to the release docs checklist

[bastianallgeier]

Will our error response code be even sent before this?

[bastianallgeier]

Sorry, that was a stupid question. Our Response class is taking care of it in the handler. Should have checked out the entire code of the file.