Searchable and viewable calendars

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

At Nextcloud we are used to that everyone shares their calendar with everyone. This makes it easy to coordinate appointments with external people if I can quickly lookup the calendar of a colleague. Having the option to enable additional calendars of your colleagues and having a joint few makes it easier to find empty slots that work for everyone than the "free-busy" feature. Especially if I don't want to setup a meeting but just want to tell someone else which dates should work for a meeting. Also it is sometimes helpful if I can search for a specific event in a calendar of a colleague.

But with the growth of Nextcloud this comes to a limit. The number of shared calendars gets more and more, caldav sync becomes bigger and bigger and they also "spam" other stuff like the task app, etc.

Describe the solution you'd like

• Setting below "Internal link" in the "Edit calendar" modal: "Show calendar to registered accounts in the 'Open calendars' dialog"
  • Place it in this menu even though the calendars will show in the "Shared calendars" entry, because otherwise people will have to look through too many menus to find what they are looking for.
• Entry "Add open calendars" in the "+" menu, above "New subscription from link"
  • Opens a dialog "Add open calendars" for listing and adding open calendars

Original idea

Describe alternatives you've considered

No response

Additional context

No response

Start by tracing the existing Edit calendar modal and the "+" menu, then review how shared calendars are listed and added. Done means registered users can mark calendars open, search and add them through the "Add open calendars" dialog, and view the selected calendars without relying on broad CalDAV sharing.