feat: add Declarative Web Push message support

[wapacro]

Hi there 👋

Apple proposed to amend the existing specifications around Web Push with a model for Declarative Web Push notifications and already implemented this for Safari 18.4 on macOS, iOS and iPadOS. From their blog:

Declarative Web Push allows web developers to request a Web Push subscription and display user visible notifications without requiring an installed service worker. Service worker JavaScript can optionally change the contents of an incoming notification. Unlike with original Web Push, there is no penalty for service workers failing to display a notification; the declarative push message itself is used as a fallback in case the optional JavaScript processing step fails.

Declarative Web Push is more energy efficient and more private by design. It is easier for you, the web developer to use. And it’s backwards compatible with existing Web Push notifications.

W3C is actively working on getting this standardized - the core specs are already merged at w3c/push-api#385, although it's still a working document.

This pull requests introduces the ability to (optionally) send Declarative Web Push messages with Laravel. Since these are by design backwards compatible, they can already be used even when targeting browsers other than Safari. There are also no breaking changes for existing generic Web Push deployments.

References

• https://www.w3.org/TR/push-api/
• https://whatpwacando.today/declarative-web-push
• https://webkit.org/blog/16535/meet-declarative-web-push/
• feat: add contentType option web-push-libs/web-push-php#433