fix(developers): Document new notification exceptions

Signed-off-by: Joas Schilling <coding@schilljs.com>

developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_30.rst

@@ -76,9 +76,23 @@ In this release support for PHP 8.0 was removed. Follow the steps below to make
 Added APIs
 ^^^^^^^^^^
 
+- ``OCP\Notification\IncompleteNotificationException`` is thrown by ``OCP\Notification\IManager::notify()`` when not all required fields have been set on the ``OCP\Notification\INotification`` object
+- ``OCP\Notification\IncompleteParsedNotificationException`` is thrown by ``OCP\Notification\IManager::prepare()`` when no ``OCP\Notification\INotifier`` handled the ``OCP\Notification\INotification`` object
+- ``OCP\Notification\InvalidValueException`` is thrown by ``OCP\Notification\IAction::set*()`` and ``OCP\Notification\INotification::set*()`` when the value did not match the required criteria
+- ``OCP\Notification\UnknownNotificationException`` should be thrown by ``OCP\Notification\INotifier::prepare()`` when they didn't handle the notification
+
 Changed APIs
 ^^^^^^^^^^^^
 
+- ``OCP\Notification\IAction::set*()`` (all setters) throw ``OCP\Notification\InvalidValueException`` instead of ``\InvalidArgumentException`` when the value does not match the required criteria.
+- Calling ``OCP\Notification\IAction::setLink()`` with a relative URL is deprecated and will throw ``OCP\Notification\InvalidValueException`` in a future version.
+- ``OCP\Notification\IApp::notify()`` throws ``OCP\Notification\IncompleteNotificationException`` instead of ``\InvalidArgumentException`` when a required field is not set before notifying.
+- ``OCP\Notification\IManager::prepare()`` throws ``OCP\Notification\IncompleteParsedNotificationException`` instead of ``\InvalidArgumentException`` when a required field is not set after preparing a notification.
+- ``OCP\Notification\INotification::set*()`` (all setters) throw ``OCP\Notification\InvalidValueException`` instead of ``\InvalidArgumentException`` when the value does not match the required criteria.
+- Calling ``OCP\Notification\INotification::setLink()`` with a relative URL is deprecated and will throw ``OCP\Notification\InvalidValueException`` in a future version.
+- Calling ``OCP\Notification\INotification::setIcon()`` with a relative URL is deprecated and will throw ``OCP\Notification\InvalidValueException`` in a future version.
+- ``OCP\Notification\INotifier::prepare()`` should no longer throw ``\InvalidArgumentException``. ``OCP\Notification\UnknownNotificationException`` should be thrown when the notifier does not want to handle the notification. ``\InvalidArgumentException`` are logged as debug for now and will be logged as error in the future to help developers find issues from code that unintentionally threw ``\InvalidArgumentException``
+
 Removed APIs
 ^^^^^^^^^^^^