refactor: enable code quality level 34 for rector

[samsonasik]

Description

Applied ExplicitReturnNullRector to add explicit return null to method/function that returns a value, but missed main return.

void in union should not happen.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[samsonasik]

Ready for review 👍 , while doesn't change native type, this can goes to 4.6 branch if needed since it change docblock returns from allowed union void to nullable union and may cause phpstan notice on user that override it.

[neznaika0]

In Filters, you can remove PHPDoc @return. It is inherited from the interface and is superfluous.

[samsonasik]

On child classes, more specific returns is ok, the parent interface allow @return RequestInterface|ResponseInterface|string|null on before() method.

[paulbalandan]

Why are we now returning $response in the after() of the filters?

[neznaika0]

Why are we now returning $response in the after() of the filters?

Response return in system/CodeIgniter.php and other places:

$possibleResponse = $this->runRequiredBeforeFilters($filters);