fix: make all implicitly-nullable parameters explicit (PHP 8.4 deprecation)

[kiuka]

Problem

Several methods declare a typed parameter with a null default but no explicit ? — relying on the implicit conversion to a nullable type. PHP 8.4 deprecates this (E_DEPRECATED), emitted when the declaration is loaded (not when the method is called), so consumers on PHP ≥ 8.4 get, e.g.:

Struzik\EPPClient\Response\ResponseInterface::get(): Implicitly marking parameter $contextNode as nullable is deprecated, the explicit nullable type must be used instead

Fix

Make every implicitly-nullable parameter in src/ explicit. There are four, all covered by this PR:

Location	Before	After
Request/Session/LoginRequest::setNewPassword()	string $newPassword = null	?string
Request/Contact/UpdateContactRequest::setDisclose()	Disclose $disclose = null	?Disclose
Response/ResponseInterface::get()	\DOMNode $contextNode = null	?\DOMNode
Response/ResponseInterface::getFirst()	\DOMNode $contextNode = null	?\DOMNode

After this, no implicitly-nullable parameters remain in src/.

Why the ResponseInterface ones matter in practice

Because the deprecation fires when the interface is loaded, it's not just cosmetic. Any consumer that parses EPP responses inside an error-to-exception handler has the notice promoted to a fatal error. Concretely, struzik-vladislav/epp-socket-connection wraps its socket IO in an E_ALL error handler (to turn socket/TLS warnings into exceptions); on PHP 8.4+ this implicit-nullable deprecation is raised while reading the server greeting and surfaces as ConnectionException: Can not open connection to the EPP server — i.e. every EPP connection breaks. AbstractResponse already uses ?\DOMNode, so the interface was also inconsistent with its own implementation.

Compatibility

?Type is valid on the full supported range (php: ^7.4|^8.0); behaviour is unchanged. No test changes required.

[kiuka]

Expanded this PR beyond the original one-line LoginRequest change: I found three more implicitly-nullable params (ResponseInterface::get()/getFirst(), UpdateContactRequest::setDisclose()) and fixed them in the same PR, so src/ is now clean. The ResponseInterface ones are the impactful ones — on PHP 8.4+ they break every EPP connection when responses are parsed under epp-socket-connection's E_ALL error handler (the deprecation becomes a fatal ConnectionException). Title/description updated accordingly.

[struzik-vladislav]

Hi @kiuka
Thanks for your PR! Please recheck the EPP connection issue. It must be solved.