Select all event participants for push notifications

One-sentence description

Easily send a push notification to everyone registered for an event.

Motivation

We don't want to bother every person with each push notification. But we do sometimes want to send a push notification to members about a certain event (such as change of location). But selecting all members by hand is not ideal either.

Desired functionality

The ability to send a push notification to everyone registered for an event.

Suggested implementation

Either the possibility to make event-specific push notifications (and maybe even give the event organizer permissions to send those). But the easier way would probably be some new selection filter thingy when adding users to a message, where you can filter on participants for a specific event.