Permission not replicated correctly on CalDav client

When sharing a calendar by setting full permissions on items but read-only on the folder, items cannot be added or changed on the CalDav client (DavX5 on Android). Read-only permission is also received on elements.

Steps to reproduce

• share a calendar with full permissions on items and read-only on the folder
• configure CalDav synchronization on the device (via DavX5) for the user who receives the shared calendar
• on the device, activate the calendar received in sharing
• on the device add or modify an event within this calendar

Expected behaviour

• you can add or edit events on the calendar

Actual behaviour

• it is not allowed to make changes or add events on this calendar (permission denied)

NOTE: The problem is not present if the calendar is synchronized on the device via EAS

Thanks to Nicola Remedi (Ref. #102268)