improve: add queue method to pending mail

[albertcht]

No description provided.

[Copilot]

Pull request overview

This PR adds queue() and later() methods to the PendingMail class to enable queuing mail messages when using the pending mail fluent interface, and updates the Mailable class to properly handle nullable mailer names by changing from an empty string default to null.

Key Changes:

• Added queue() and later() methods to PendingMail for queuing mail operations
• Changed Mailable::$mailer property from string with empty string default to nullable ?string with null default
• Updated MailFake::prepareMailableAndCallback() parameter type to accept callable|string|null

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/mail/src/PendingMail.php	Added queue() and later() methods to support queuing mails through the pending mail interface
src/mail/src/Mailable.php	Changed $mailer property and mailer() method to accept nullable string for better semantic representation
src/mail/src/Contracts/Mailable.php	Updated interface to accept nullable mailer name in mailer() method
src/support/src/Testing/Fakes/MailFake.php	Updated parameter type to accept string addresses in addition to callable

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[Copilot]

The parameter type order is inconsistent with the MailQueue interface and Mailer class implementation. The order should be DateInterval|DateTimeInterface|int instead of DateTimeInterface|DateInterval|int to match the interface definition and maintain consistency across the codebase.

Suggested change

	public function later(DateTimeInterface|DateInterval|int $delay, MailableContract $mailable): mixed
	public function later(DateInterval|DateTimeInterface|int $delay, MailableContract $mailable): mixed