Clarify public sharing link

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

Apparently it is not possible to share a Nextcloud calendar to the Google Calendar web front end.

You can integrate the calendar https://website.com/apps/calendar/p/xxxxxxxxxxxxxx in Google Calendar, but no appointments are displayed.

Describe the solution you'd like

It should be possible to release the calendar as an ICS file so that it can be integrated into other calendars.

Describe alternatives you've considered

No response

Additional context

Since you can only send appointments to external people inconveniently (ics as an attachment, no updates when appointments change) and also cannot share them with external people, the Nextcloud calendar is unfortunately only suitable for internal purposes or for individual people.

That's why I can't completely switch to my Nextcloud.

Unfortunately, I can't even integrate the Google calendar in the Nextcloud and manage the appointments here, because you can only integrate them as read-only.

Start by reproducing the public calendar link in Google Calendar and compare it with the requested ICS/webcal behavior. Read the calendar sharing and CalDAV-related entry points, then check the RFC 5545 expectations referenced by the repository topics. Done means an externally shared calendar can be integrated and its appointments appear in Google Calendar.