feat: dispatching AnnouncementPublished event

[madbob]

Added an Event to notify other apps (both local than remote, using webhooks) about announcement publishing.

Ref #1050 (as the event can be listened by the mohamedsakhri/nextcloud-announcementbanner app and display the attached announcement as preferred).

[nickvergessen]

I would prefer if it's only this instead of exposing an internal entity. Sorry didn't see that before.

So I would have the constructor of the event take those strings and integers instead and not have a getAnnouncement method

[madbob]

Initially I had the same idea, then I saw other apps (e.g. in Mail) just dispatching the whole involved Entity.

Anyway, I would suggest to keep IWebhookCompatibleEvent implementation separated by the behavior of the event. Maybe, something like

public function getData() {
  return $this->serialize();
}

public function getWebhookSerializable() {
  return $this->serialize();
}

private function serialize() {
  return [
    'subject' => $this->announcement->getsubJect(),
    etc...
  ];
}

Just to avoid breaking all Listeners in the unlikely event IWebhookCompatibleEvent interface will change.

[madbob]

(And I just realized I mistyped all entity's getters method... Not my best performance, today...)

[nickvergessen]

Or simply:

public function getWebhookSerializable() {
  return [
    'subject' => $this->announcement->getSubject(),
    etc...
  ];
}

Ne need to duplicate a getData method