Fix PHP 8.4 / 8.5 deprecations (implicit nullable params, curl_close)

[jpxd]

This makes the library clean under PHP 8.4 and 8.5 with a minimal, behaviour-preserving diff (the curl transport is otherwise untouched).

PHP 8.4 — implicit nullable parameters

Parameters typed string $x = null are implicitly nullable, which is deprecated in PHP 8.4. Added an explicit ? to all affected signatures:

• EndMeetingParameters::__construct()
• IsMeetingRunningParameters::__construct()
• DeleteRecordingsParameters::__construct()
• UpdateRecordingsParameters::__construct()
• InsertDocumentParameters::__construct()
• GetRecordingTextTracksParameters::__construct()
• PutRecordingTextTrackParameters::__construct()
• DocumentableTrait::addPresentation() ($attributes)

PHP 8.5 — curl_close()

curl_close() is deprecated as of PHP 8.5 (it has had no effect since PHP 8.0, where the curl handle became a CurlHandle object freed by the garbage collector). Removed the call in sendRequest().

Bonus: presentation serialization fixes

While adding ? to addPresentation() I noticed getPresentationsAsXML() was broken for presentations added without attributes/content (the existing tests/Parameters cases for URL/file presentations errored):

• null->getAttributes() fatal when no DocumentOptionsStore was passed → now guarded.
• URL-only documents serialized as <document url="...">1</document>, because !$content ?: base64_encode($content) yields true for null content → now stored as null.

These two one-liners turn the previously red tests/Parameters presentation tests green. Happy to split them into a separate PR if preferred.

Verification

• php -l clean on all files (PHP 8.5)
• Deprecation reproduction: emitted before, clean after
• tests/Parameters + tests/Responses: 18/18 green