Fix PHP 8.4 deprecations

[cedric-anne]

Implicitly nullable parameter declarations are deprecated in PHP 8.4. The proposed change is safe and is not considered by PHP as a signature change, see https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

[yakatz]

This can't pass the tests until PHP 8.4 is actually released, or it needs to specify the PHP version as 8.4-rc to use the beta version.

[cedric-anne]

Test suite fails because xdebug is not yet available for PHP 8.4.

[adoy]

PHP8.4 is release now. Would be nice to merge this PR :-)

[Mistralys]

👍 Would love to see this merged as well.

[floverdevel]

i would also really appreciate the merge of this PR :)

[androbi-com]

We would appreciate a merge too ...

[Mistralys]

FYI: As a temporary fix, it is possible to install cedric-anne's version by referencing the commit directly in your Composer configuration:

"require": {
    "apereo/phpcas": "dev-master#77309b6a7f304a5f9e351bc52d8adc831989734f"
}

Where the hash is the latest commit as of today.

Note that if you also use roave/security-advisories, this will not be installable.