Allow to disable event reminders on a per-user basis

Is your feature request related to a problem? Please describe.

Per default, NextCloud sends calendar event notifications (e.g. via the desktop app) for all events. It is only possible to disable this server-wide (see #2057).

Describe the solution you'd like

I'd like to have the ability to disable this for my account, only.

Optionally: allow configuring this on a per-calendar basis. But maybe that's overkill. I actually assume most people use a separate calendar app anyway (and I expect those to have such a feature already)

(Maybe: Being able to set this within the desktop app "don't show calendar notifications on this device". That would require a separate ticket over at nextcloud-desktop right?)

Describe alternatives you've considered

(Ask the admin to) disable it for all users. Obviously, this is not always possible.

Additional context

No response

Start by reviewing the server-wide event-notification behavior referenced in issue #2057 and tracing how calendar reminders are configured and delivered. Define the account-level setting and its interaction with existing users before considering the optional per-calendar or desktop-app variants; done means one user can disable reminders without changing them for others.