Send upcoming events monthly #feature #flow

Is your feature request related to a problem? Please describe.
Not everyone of my users is having a look onto our cloud regularly. Also not all of them able to install talk and the nc client on smartphone. Still I want to send them all events on a regular basis, without spamming them.

Quite honest, I'm trying to send them their events manually, but failing quite often due to a bunch of other tasks.

Describe the solution you'd like
Send an email with all upcoming events for the next month on 24th of every month or so. There also should be a switch to turn that off on a user basis.

Describe alternatives you've considered
In our use case, there could also be an email send out with our civicrm system, which also holds a few events, but nextcloud contains all of them and also in nextcloud everyone with the permission is able to add events, which makes nc the better option to implement this.

Additional context
Small bounty of 40 € is possible.

The issue names no files, tests, or entry points, so first locate the calendar event and user-settings areas related to email notifications. Done should include a monthly email containing the next month’s events and a per-user switch to disable it, with tests covering both behaviors.